Franklin kicked his 100th goal for the home-and-away season against Carlton in round 22 at Etihad Stadium, becoming the first player to kick 100 goals in a season since Tony Lockett in 1998, the first player to kick 100 goals in a year since Fraser Gehrig in 2004, the first Hawthorn player since Jason Dunstall in 1996, as of 2020, the last player to kick 100 goals in a year. Upon reaching the milestone, thousands of supporters stormed the field and formed a large huddle around Franklin, who was promptly ushered from the field and into the change rooms until the supporters had cleared. Prior to the match, the AFL had warned of a $6000 fine for every person who jumped the fence. He also was the first player of Aboriginal descent to achieve this. He then added to his tally by kicking another eight goals in the qualifying final against the Western Bulldogs, equalling Dermott Brereton’s record for the most goals kicked by a Hawthorn player in a finals match. He kicked just one goal against St Kilda in the preliminary final, before Hawthorn went on to win the premiership. Although Franklin did not play a large part in the grand final, his two goals brought his season tally up to 113 goals. Franklin was named as full forward in the 2008 All-Australian team, his first ever selection; he then received his first Peter Crimmins Medal for his outstanding season.

At the age of 15, he won a sports scholarship and boarded at Wesley College. He played one senior game for the Perth Football Club in 2004, kicking one goal, and represented Western Australia at the 2004 AFL Under 18 Championships.

After attending draft camp and showing promise, Hawthorn selected Franklin with their second pick, number five overall, in the 2004 AFL Draft. In a 2012 interview on the Fox Footy program On the Couch, Franklin admitted that his “free spirit” probably scared a few clubs away from selecting him that year. Franklin made his debut in round 1 of the 2005 season against Sydney at the Sydney Cricket Ground and showed a strong presence up forward throughout the year, kicking 27 goals in 20 games.

After injuring his ankle and hand early in the 2006 pre-season, Franklin made his way back to senior level through the VFL and returned in round 9 against the Sydney Swans. In round 12, he kicked six goals against Richmond, in what was his breakout game. On 13 July 2006 Franklin signed a two-year deal to remain at Hawthorn after being linked with clubs such as Essendon, Fremantle and the West Coast Eagles. Another six-goal game late in the season prompted predictions of Franklin to be the next big-name forward in the AFL.

In 2007, Franklin finished the home-and-away season with 63 goals, finishing third in the Coleman Medal behind Brisbane Lions co-captain Jonathan Brown and Fremantle captain Matthew Pavlich. Franklin’s tally included a career-high nine goals against Essendon in round 6. However, in round 21 against the Western Bulldogs, he kicked eleven behinds with his two goals. Only Richmond’s Jack Titus and St Kilda’s Dave McNamara have kicked more behinds in a game without managing more than two goals. Franklin was instrumental in Hawthorn’s elimination final win over the Adelaide Crows, kicking seven goals in his finals debut, including the match-winning goal from outside fifty metres with seven seconds remaining in the match. Hawthorn were eliminated from the finals the following week by North Melbourne.

2008 saw Franklin establish himself as one of the elite players in the competition in what proved to be his career-best season, and he won his first Coleman Medal with 102 goals in the home-and-away season. His season-high haul of nine goals came once again against Essendon in round 11. He also played for the Dream Team in the AFL Hall of Fame Tribute Match, kicking four goals.

In bringing up his 50th goal for the season, against St Kilda in round 18, Franklin brought up 50 goals in a season for the tenth time. He was the first player to achieve this feat since Matthew Lloyd in 2008, and one of only nine players in the history of the game to ever do so; the other eight players had all kicked over 900 goals in their careers. Franklin saved his best performance of the season – and arguably his best for the Swans – for the eve of finals, recording 25 disposals, ten marks and ten goals against Carlton at the SCG in round 23. This was only the second time in Franklin’s career that he had kicked ten or more goals, and it took him to 69 goals for the home-and-away season. At the end of the previous round, Franklin had trailed Josh Kennedy, winner of the last two Coleman Medals, by five goals, but the dominant performance saw him eventually finish four goals ahead of Kennedy, sealing Franklin’s fourth Coleman Medal; it also continued Franklin’s trend of winning a Coleman Medal every three years.

In round 13, Franklin effectively dragged Hawthorn over the line for a win against their arch-rival in Essendon. He kicked five goals for the match, but his last two were the standouts–the final one in particular, a goal from the boundary line on a tight angle after having run from half-back, which was later chosen as Goal of the Year. Franklin kicked five goals in Round 17 against St Kilda after returning from an ankle injury; despite his performance, the Saints forced a draw during the final seconds of the match. In round 22, Franklin kicked six goals against Collingwood, helping the Hawks clinch a three-point come-from-behind victory against the eventual premiers. It was the first time that he had kicked more than five goals since 2008. Frankin was named as centre half-forward in the 2010 All-Australian team, his second selection.

After a moderately good year in 2010, Franklin had a consistent start to the 2011 season. In round 8 against the Sydney Swans at the SCG, Franklin kicked his 400th goal for Hawthorn in a six-goal outing as the Hawks beat the Swans by 46 points. He continued his consistent goalkicking form for the remainder of the year, including a season-high eight goals in a club-record 165-point win against a young Port Adelaide side at the MCG in Round 21. Franklin went on to win his second Coleman Medal that year with 71 goals, despite spending a significant amount of time further up the ground.

Franklin was Hawthorn’s sole target up forward in their qualifying final loss to the Geelong Cats, kicking four goals. However, in the fourth quarter, he landed heavily in a marking contest and hyperextended his knee. While footage of the incident suggested possible damage to his anterior cruciate ligament, scans later revealed that he had instead suffered bone bruising and bleeding; nevertheless, most observers considered Franklin’s season to be over following the loss. However, he returned the following week against the Sydney Swans, kicking another four goals and playing an important part in the Hawks’ eventual win. Despite spending time in hospital with a virus in the lead-up to the preliminary final against Collingwood, Franklin was a constant danger, kicking three goals, including a dribble kick in the forward pocket from a tight angle, which almost sealed victory for Hawthorn until Collingwood kicked a late goal and won the match, eliminating the Hawks. Franklin was named in the 2011 All-Australian team, his third selection and second as full forward.

Franklin returned against Sydney at the SCG in round 22, kicking four goals in a seven-point come-from-behind victory against the eventual premiers, including three in the second quarter. Franklin played a minor role in the finals series that year, but kicked a goal late in the last quarter of the preliminary final against Adelaide which sealed the game for the Hawks, allowing them to qualify for the grand final against Sydney, where Franklin kicked three goals in a losing side. Franklin was named in the 2012 All-Australian team, his fourth selection and second as centre half-forward.

Franklin played in the 2013 AFL Grand Final in which Hawthorn defeated Fremantle; this was the second time that he had played in a Hawthorn premiership winning side. Despite this, his season was dominated by media speculation over his contract situation, and playing in a second premiership at Hawthorn only strengthened rumours of his impending departure, with many believing that he was set to finish his career at Hawthorn on a high note.

On 1 October 2013, after months of speculation dating back to before the start of the season, Greater Western Sydney shocked the football public by announcing that it had withdrawn its offer of $1.2 million per year for six years, saying that the club was of the belief that Franklin was set to sign with the Sydney Swans. The Sydney Swans’ chairman, Andrew Ireland, said later that day that the contract offered to Franklin was a nine-year deal worth $10 million, and that Franklin’s management first approached Sydney about the move shortly after the 2012 AFL Grand Final, when Franklin played in a losing side against the Swans. The next day, Franklin said that he did not make his decision to move to Sydney “until the last minute”. He also said, “I’m looking forward to getting up to Sydney. It’s a great footy club and, as I said, I had to pack my bags up at Hawthorn and saying goodbye to the boys is something very tough, and upsetting, too”. Franklin’s manager at the time, Liam Pickering, also revealed that the nine-year contract was so back-ended that he would be making less money with the Swans in 2014–15 than he was at Hawthorn in 2013.

Franklin officially joined the Sydney Swans on 8 October 2013, a week after the move was first announced, after Hawthorn decided against matching the offer made to the restricted free agent. The next day, Franklin was unveiled by the Swans at the SCG. Later in October, Franklin travelled to Ireland with the Australian International Rules team for the 2013 International Rules Series. It was the first time that Franklin had represented Australia in international rules football, and he managed one over in the first match of the two-test series. Following the first match, he travelled back to Australia for the wedding of his former teammate Brent Guerra, and was unable to participate in the second match.

Franklin continued his outstanding form throughout the season (despite kicking waywardly in both matches against his former side in Hawthorn, registering 2.7 and 3.5) and went on to win his third Coleman Medal, kicking 67 goals in 19 matches during the home-and-away season. Franklin also played his 200th game during the season, kicking a season-high nine goals in round 19 against St Kilda at the SCG. Franklin was named in the 2014 All-Australian team, his fifth selection and third as full forward; he then went on to finish equal-second with Gary Ablett, Jr. in the 2014 Brownlow Medal count on a career-high 22 votes (the most votes ever polled by a Coleman Medallist), beating the tally of 20 votes he achieved in his other Coleman Medal-winning years of 2008 and 2011. Franklin was one of the Swans’ best players throughout the finals series, and kicked four goals in the 2014 AFL Grand Final loss to Hawthorn – his highest ever tally in a grand final.

Franklin reasserted his decade-long dominance against Essendon in the elimination final, kicking four goals in a second-quarter burst despite suffering a corked thigh in the first quarter, but was quiet in the semi-final loss to Geelong, kicking three behinds. This marked the earliest exit from a finals series by a team that Franklin has played in (excluding 2015, when he missed the finals series) since 2010. Franklin was named in the 2017 All-Australian team, his seventh selection and his fourth at centre half-forward; it was also the first time that he had achieved consecutive All-Australian selections since 2012, when he had achieved the accolade three years consecutively. Franklin also polled an equal career-high 22 votes in the 2017 Brownlow Medal count, equalling the record number of votes achieved by a Coleman Medallist that he polled in 2014.

Franklin was one of the Swans’ best players during the finals series, despite only contributing seven goals across the four finals, and was among their best players in the 2016 AFL Grand Final loss to the Western Bulldogs. Franklin was named in the 2016 All-Australian team, his sixth selection and his third as centre half-forward. By season’s end, he was the twelfth-highest goalkicker in VFL/AFL history, having overtaken greats such as Wayne Carey, Peter Hudson, Stephen Kernahan, Barry Hall and Kevin Bartlett during the home-and-away season.

Franklin married former Miss Universe Australia model and Nine Network presenter Jesinta Campbell on 4 November 2016. They have one daughter together.

Franklin was held goalless for only the second time that year in the elimination final loss to Greater Western Sydney as he dealt with a hip problem. His total of 57 goals for the year was his second-lowest in a season since 2006, however he still averaged the most goals per game during the home-and-away season. Franklin was named as captain in the 2018 All-Australian team, which was also his fifth selection at centre half-forward, third in succession and record-equalling eighth overall; this was despite missing four games and hardly being able to train due to injury, which Franklin described as being “frustrating”. He later had surgery on his late-season groin injury, keeping him out of training for the rest of the year.