Schwarzer’s first club was Colo Cougars in Richmond, New South Wales. He started his professional career at age 19 with Marconi Stallions in the National Soccer League. He left the Sydney-based club to play in Germany in 1994 with Dynamo Dresden and 1. FC Kaiserslautern. He then travelled to England to play for Bradford City in 1996, where he eventually joined Middlesbrough in February 1997.

Schwarzer made his international debut for Australia against Canada in Edmonton in a 1994 World Cup qualifier in 1993. He came on as a substitute for Milan Blagojevic after first-choice Robert Zabica was sent off 15 minutes into the match. In the return leg in Sydney, he made headlines when he saved two penalties to send Australia to the final phase of qualifying against Argentina. Schwarzer did not play in these matches, and Australia were defeated 2–1 on aggregate.

Schwarzer made his debut for Middlesbrough against Stockport County in the League Cup semi-finals on 26 February 1997. He featured in the final against Leicester City, which ended as a 1–1 draw, but was injured for the replay. He also played in the 1998 League Cup final against Chelsea, but was unable to prevent Middlesbrough from slipping to a 2–0 defeat. He was part of the side, however, who beat Bolton Wanderers 2–1 to win the final six years later, despite making an error described by BBC Sport as a “howler” which allowed Kevin Davies a consolation goal for Bolton.

He was instrumental in Australia’s qualification for the 2006 World Cup, in the play-off against Uruguay. After Uruguay won the first leg 1–0 in Montevideo, Australia won 1–0 in Sydney on 16 November 2005. In the penalty shoot-out, Schwarzer saved two penalties to see Australia victorious 4–2.

Schwarzer was granted a transfer request by Middlesbrough on 6 January 2006 and sought to join a new club, but he withdrew his request on 20 January 2006, and rejoined the team. A fractured cheekbone sustained against West Ham United, however, looked like it had ruled Schwarzer out for the rest of the season, but he returned for the UEFA Cup final against Sevilla, albeit playing with a protective mask. When he played in Middlesbrough’s 1–0 victory over Portsmouth on 29 December 2007, he became the Premier League’s longest-serving foreigner at one club, surpassing Dennis Bergkamp’s record of 315 matches. Schwarzer’s final Middlesbrough appearance came in an 8–1 victory over Manchester City on the final day of the 2007–08 Premier League season, after he had made 446 appearances in all competitions.

Schwarzer played in all of Australia’s matches in the 2007 AFC Asian Cup. Although he made two good saves in the opening match against Oman, which finished as a 1–1 draw, he made an error which led to a goal in the 3–1 loss to Iraq. In the quarter-final, he could not match Japanese goalkeeper Yoshikatsu Kawaguchi during the penalty shootout, which saw the Socceroos get knocked out of the competition in their debut at the tournament. Schwarzer said that the penalty shootout in the Asian Cup quarter-finals was the first penalty shoot-out in his career that he had ever lost.

Schwarzer’s contract with Middlesbrough expired in June 2008, and although he was offered a new contract, manager Gareth Southgate had to plan a future with a new goalkeeper as, on 21 May 2008, Schwarzer signed a two-year contract at Fulham, ending an 11-year association with the Teesside club. Schwarzer revealed in an interview with The World Game that he had received offers from Bayern Munich and Juventus but declined their offers because they could not guarantee him the position as the number-one goalkeeper.

In 2009, Schwarzer was awarded the Medal of the Order of Australia.

He played an important role in Fulham reaching the Europa League final in 2010, but Schwarzer lost his second European final with a narrow defeat to Atlético Madrid.

Following his performances during the 2009–10 season, Arsenal manager Arsène Wenger attempted to sign Schwarzer. It was reported that a bid of around £2 million in May 2010 had been made for Schwarzer and a second bid of around the same value had been made in August 2010; however both were rejected by Fulham.

On 13 August 2010, Fulham manager Mark Hughes revealed that Schwarzer had handed in a transfer request, which Hughes had rejected. On 31 August 2010, it was reported that Arsenal had made a last-ditch bid of around £4 million to bring Schwarzer to the Emirates Stadium before the transfer window closed, however Hughes denied that any approach was made.

Schwarzer saved an 89th-minute Shao Jiayi penalty against China in Australia’s 0–0 draw in the 2010 World Cup qualifier in March 2008, continuing his record of stopping penalty kicks. He received his second yellow card of the campaign against Qatar in Doha, in which Australia were 3–1 winners, leading to him being suspended for the following match against China.

He was the country’s first-choice keeper for all three matches of the group stage in the 2010 World Cup in a group composed of Australia, Germany, Ghana and Serbia. In the first match, Australia were crushed 4–0 by the Germans, but they recovered with a 1–1 draw against Ghana in the next game. In the final match, Australia beat Serbia 2–1, thus finishing third in the group with four points, just missing out on qualification to the round of 16 on goal difference with Ghana.

Schwarzer signed a contract extension with Fulham on 18 January 2012, committing himself to the club until at least the summer of 2013.

Schwarzer made a notable injury-time penalty save against Mikel Arteta in January 2013 to help Fulham earn a 3–3 draw against Arsenal. In April 2013, he made his 500th Premier League appearance in a game against Arsenal, and became the first non-British or Irish player to do so in the process.

On 5 June 2013, Schwarzer announced he was leaving Fulham following the arrival of Maarten Stekelenburg. He said, “I’ve been hearing that for a while,” he said of Stekelenburg’s arrival. “It’s no great surprise and I’ll be looking for another club.” Schwarzer was one of 12 players released by Fulham at the end of the 2012–13 Premier League season.

On 9 July 2013, Schwarzer signed a one-year contract with Fulham’s West London rivals Chelsea on a free transfer. He has been quoted saying, “It’s one of the biggest and best clubs in the world, and it’s an honour to sign for Chelsea. I didn’t take much convincing to come here.” He made his competitive debut in a 2–0 away victory over Swindon Town in the League Cup. In Schwarzer’s second appearance with Chelsea, he kept another clean sheet, as Chelsea eliminated Arsenal from the League Cup in a 2–0 victory on 29 October.

After the tournament, Schwarzer declared his interest in playing at the 2014 World Cup, at which time he would be 41 years old. On 5 November 2013, however, he announced his retirement from international level.

Schwarzer became the oldest player to represent Chelsea in the Premier League when he played against Sunderland on 19 April 2014, aged 41 years and 195 days old. He became the club’s oldest ever player by some margin, overtaking Graham Rix, whom last played for Chelsea at the age of 37 years and 203 days. On 22 April, he replaced the injured Petr Čech in the first half of a Champions League semi-final against Atlético Madrid, and kept the score at 0–0. On 27 April, he started against Liverpool at Anfield, a crucial game for Chelsea to stay in the title race. He kept a clean sheet and made some outstanding saves to deny Liverpool from equalising, with Chelsea winning the game 2–0. His clean sheet against Liverpool was his 150th Premier League clean sheet, a feat only two other goalkeepers have achieved so far, those goalkeepers being Čech and David James.

Schwarzer was included on the list of players released by Chelsea at the end of the season, but he eventually signed a new one-year contract with the club, on 30 June 2014.

On 6 January 2015, Schwarzer moved to Premier League side Leicester City on a free transfer as cover for the injured Kasper Schmeichel, after signing an 18-month deal. Chelsea manager José Mourinho praised Schwarzer’s contribution to his former club, and stated that Chelsea would miss him. Schwarzer made his competitive debut for Leicester on 24 January in a 2–1 away win over Tottenham Hotspur in the fourth round of the season’s FA Cup, becoming Leicester’s oldest ever player in doing so. He made his Premier League debut for Leicester one week later in a 3–1 loss to Manchester United at Old Trafford. Schwarzer made eight appearances in his first season at the King Power Stadium, of which six were in their successful campaign to avoid relegation from the Premier League.