Klose was born in the Silesian city of Opole, Poland. Both of his parents were professional athletes. His father, Josef Klose, was also a professional footballer who played for Odra Opole, before leaving Poland in 1978 to play for French club Auxerre. His mother, Barbara Jeż, was a member of the Poland women’s national handball team. As an ethnic German and German national, Josef Klose was an Aussiedler whose family had remained behind when Silesia was ceded to Poland after World War II and decided to bring his family to West Germany. In 1986, then eight-year-old Miroslav joined his father in Kusel, Rhineland-Palatinate, knowing only two words of German. Klose developed his footballing skill and passion with local club SG Blaubach-Diedelkopf, which at the time was in the West-German seventh division. He was also an apprentice carpenter.

In 1998, Klose’s professional career began at age 20 with a switch to the reserves at former Bundesliga outfit FC Homburg. Twelve months later, he moved to 1. FC Kaiserslautern. He played for the second team and made his first appearance in the Bundesliga in April 2000. He scored 16 goals in 2001–02 season and was shy of only two goals to become the top scorer.

Klose’s consistency as a goal-scorer in his first Bundesliga season at 1. FC Kaiserslautern earned him attention. In January 2001, then-head coach of the Poland national team, Jerzy Engel, travelled to Germany to persuade Klose to choose to represent Poland. This request was declined by Klose, who said, “I have a German passport, and if things are still running this way, I have a chance to play for Rudi Völler.” Klose’s hopes were justified, as he would soon score for Germany.

Klose’s international debut came on 24 March 2001 in a 2002 FIFA World Cup qualifier against Albania; in the 73rd minute, Germany head coach Rudi Völler put him in as a substitute. Two minutes from time, he headed home the winner in a 2–1 victory for Germany, and celebrated with a front-flip. Four days later, in his second match, Klose helped Germany temporarily lead their qualification group, as he came on in the 67th minute and scored in the 3–2 win against Greece in the 82nd minute, making it two crucial goals in only 33 minutes on the pitch. Two hat-tricks against Israel and Austria in friendlies prior to the upcoming World Cup were enough to establish him in Germany’s starting line-up for the tournament.

In March 2004, Klose signed a four-year contract with Werder Bremen for a €5 million ($6.2 million) transfer fee. He made his league debut on 6 August 2004 as a substitute for Paraguayan striker Nelson Valdez in a 1–0 home win against Schalke 04. On 29 August 2004, Klose scored his first goal, an equaliser, but the Bremen team lost 2–1 at home against VfL Wolfsburg.

Throughout his career, Klose often stood out for his fair play and honesty in addition to his skill and goalscoring as a footballer. On 30 April 2005, while playing for Werder Bremen, Klose refused to accept a penalty given against Arminia Bielefeld as he felt the decision was incorrect. He was later given a fair play award for his actions, although he had mixed feelings about the award, stating, “It’s a big honour for me to receive this award, but I am also a bit irritated. For me, it was something you should always do. I would do it again – always.”

Klose and his wife Sylwia have twin sons, Luan and Noah. In a 2007 interview with Der Spiegel, he stated that at home, he and his wife speak Polish to their children, who learn German in school. Klose relinquished Polish citizenship at age 18, opting to keep his German passport.

On 7 June 2007, Klose confirmed that he would leave Werder Bremen for Bayern Munich either before the 2007–08 season or upon the expiration of his contract with the Bremen team at the end of the 2007–08 season.

On 26 June 2007, Bayern Munich club president Karl-Heinz Rummenigge confirmed his team had reached an agreement with Werder Bremen regarding the transfer of Klose. Klose completed his medical with Bayern on 28 June 2007 before signing a four-year contract.

In an interview given to Przegląd Sportowy on 9 June 2008, Klose stated the decision to play for Germany instead of Poland was not an easy one, and if Polish officials had been faster, he would be playing for Poland. Further, he added he does not regret the choice, as with Germany he has won medals in the World Cup tournaments.

At Euro 2008, Klose started the opening group stage match against Poland and assisted Lukas Podolski’s two goals in a 2–0 victory. He played the remaining two group games against Croatia and Austria with no goals of his own. He finally broke his duck during the knockout stages, scoring for Germany in the quarter-final and the semi-final against Portugal and Turkey respectively. In both matches, he scored Germany’s second goal, and both games were won 3–2. However, Klose was unable to score during the final against Spain, which Germany lost 1–0.

Klose won the first major honours of his club career at the end of his first season with Bayern, as they won the Bundesliga and the DFB-Pokal in 2007–08. In 2010, he won the 2010 DFL-Supercup, scoring a goal in the 81st minute.

Klose opened the scoring in the round of 16 match against England on 27 June 2010 with his 12th World Cup goal, equalling Pelé for fourth on the all-time list, and also notching up his 50th international goal in his 99th international game, as Germany won the match 4–1.

On 7 June 2011, with his contract about to expire, Klose did not reach an agreement with Bayern, thus leaving the club at the end of the 2010–11 season. He had scored one Bundesliga goal in 20 matches in his final season.

Klose signed a three-year contract with Italian Serie A club Lazio on 9 June 2011. He scored his first goal for Lazio in the 2012–13 UEFA Europa League play-offs and also assisted four other goals. Lazio won that match 6–0 and won the play-off 9–1 on aggregate against Rabotnički. On 9 September 2011, he made his Serie A debut in a 2–2 draw against Milan and scored a goal in the 12th minute, which was the first Serie A goal of the season. Despite having been at the club for only a few months, Lazio coach Edoardo Reja underlined his importance to the team. On 16 October 2011, Klose scored in the 93rd minute to win the Rome derby against Roma for Lazio, 2–1. However, the occasion was tainted by a small section of radical Lazio fans holding a sign adapted from a motto used by the Nazis. The sign read “Klose Mit Uns”, which means “Klose with us”. It was intended by those fans as praise for Klose, however the Nazis used the motto “God with us” and the Lazio fans’ sign featured the S’s in the same font as the logo of Adolf Hitler’s Schutzstaffel (SS). Klose had explicitly condemned the sign, saying, “[P]olitics should stay out of the stadium.”

On 10 December 2011, Klose scored twice and assisted one for Lazio in an away game against Lecce, including an 87-minute goal that gave Lazio a 3–2 victory.

On 2 September 2012, Klose scored his first Serie A goal of the season, scoring a brace in Lazio’s 3–0 home win against Palermo. On 26 September, Klose accidentally scored a goal with his hand against Napoli for Lazio, unseen by the referee. However, Klose showed great sportsmanship by informing the referee and asking to discount the goal. The referee then reversed the decision and the goal was discounted.

On 2 December, Klose scored his ninth goal of the season, securing a 2–1 victory over Parma, lifting Lazio into fourth place in Serie A. Two weeks later, on 15 December, he scored a late goal to send his side to a 1–0 victory over second-placed Internazionale, reducing the gap between the two sides in the league table to one point. On 5 May 2013, he scored five goals against Bologna before being substituted for Louis Saha in the 68th minute. It was the first time since the 1984–85 season that a player scored five goals in the same game in Serie A.

Klose started the season by playing in the 2013 Supercoppa Italiana against Juventus, which ended in a 4–0 loss at Stadio Olimpico. Klose started the league season by playing 83 minutes in team’s opening league match of the season, a 2–1 home win against Udinese and scored his first goal of the season on 31 August in a 4–1 away defeat to Juventus. He scored his second league goal of the season on 28 October during the 2–0 home victory against Cagliari.

Prior to the tournament, Klose said the 2014 World Cup would be his last one for Germany, stating he wanted one more shot at trying to win the World Cup and having done that, he was content. On 6 June 2014, in Germany’s final friendly before the World Cup against Armenia, Klose scored his 69th international goal, thus breaking Gerd Müller’s record of 68 goals and becoming Germany’s record goalscorer.

Klose scored his record-equalling 15th World Cup goal to help Germany to a 2–2 draw against Ghana on 21 June 2014, after entering the game as a 69th minute substitute for Mario Götze (who had scored Germany’s first goal) with his team trailing 2–1. This tied him with the Brazilian player Ronaldo. With this goal, Klose became the third player in history to score in four different World Cups. On 8 July, Klose scored a record 16th World Cup goal in the 23rd minute against Brazil in the semi-finals, his second goal of the 2014 World Cup. That goal gave Germany a 2–0 lead, en route to a 7–1 win over Brazil, and Klose surpassed Ronaldo’s previous record of 15 World Cup goals. Klose set another record by becoming the first player to appear in four consecutive World Cup semi-finals. Klose started in the World Cup final against Argentina, playing until the 88th minute when he was substituted for Mario Götze. Götze would score the 113th-minute goal which held up as the winning goal in Germany’s 1–0 victory over Argentina, earning Germany’s fourth World Cup title overall and first as a reunited country. Klose announced his retirement from international football one month after the final.

On 1 November 2016, Klose was hired to become part of the coaching staff of the German national team. Klose said, “I celebrated my greatest successes with the national team and it was a wonderful and unforgettable time. That’s why I’m delighted to return to the DFB. In the past few months, I have thought a lot about continuing my playing career, but also about pursuing other avenues, namely becoming a coach.”

At the end of September 2012, Klose scored a goal using his hand for Lazio against Napoli. He admitted this to the referee, who took back his decision to award the goal, spared Klose from a yellow card and shook his hand. Later that year, he was once again given a fair play award for his actions by the German Football Association, later commenting, “The referee asked me if I had touched the ball with my hand and it was not a problem for me to answer ‘yes’. There are many youngsters who watch football on TV and we are role models for them.” In 2016, he was given the Sport Ethics Award for his honesty at the University of Rome Tor Vergata, and subsequently added regarding the incident, “Napoli? For me it was easy, it’s my character. We need to set an example, … If I can even help out the referees, I will do so willingly.”

On 11 May 2018, Bayern Munich named Klose as their coach for the U-17 team. Klose signed a two-year contract until the end of June 2020.

On 7 May 2020, Klose signed a one-year contract to become the first-team assistant manager under Hans-Dieter Flick.