He was also runner-up at the 2017 Wimbledon Championships and the 2018 Australian Open, and won a silver medal at the 2020 Tokyo Olympics in the men's doubles tournament partnering Ivan Dodig.

[10][11] His father Zdenko Čilić was determined that his sons – Marin and older brothers Vinko and Goran – would have the opportunities he lacked in playing sports.

In 2005, he won the French Open title in Boys' singles, beating Andy Murray in the semifinal[13] and Antal van der Duim in the final.

In June, at the Queen's Club Championships, he beat Tim Henman in the first round after trailing 2–4 in the final set, and reached the quarterfinals, where he fell to Andy Roddick.

In the World Group playoffs in the first round of the 2007 Davis Cup, Čilić beat Benjamin Becker of Germany; however, Croatia went on to lose the tie, three matches to two.

Čilić, seeded for the first time at a Grand Slam tournament, reached the third round of the US Open, but lost to Novak Djokovic in a match that lasted almost four hours.

[20] He reached the second round of the Queen's Club Championships, an ATP World Tour 250 series event, where he was defeated by Nicolas Mahut of France.

Čilić played for Croatia in the World Group playoffs in the first round of the 2011 Davis Cup, defeating Florian Mayer in the opening singles rubber.

At Wimbledon Čilić pulled out before his second-round match claiming he had a left knee injury where he was scheduled to play Kenny de Schepper of France.

[27] However, a month later it was revealed that Čilić had pulled out due to failing a drugs test in Munich for, according to Jutarnji list daily, "incautious use of glucose.

Čilić claimed that the banned substance was ingested via Coramine glucose tablets bought at a pharmacy by a member of his team, and as a result, the independent tribunal believed that he did not intend to enhance his performance.

Čilić continued his excellent form in Delray Beach, reaching his third consecutive final of the season, where he defeated Kevin Anderson and won his 11th singles title.

Čilić returned to Queen's Club in June, where he was last year's runner-up on the grass court, however, he was knocked out by Marinko Matosevic in the first round.

Čilić successfully rebounded at Wimbledon, reached the quarterfinals for the first time, beating Paul-Henri Mathieu, Andreas Haider-Maurer, Tomas Berdych and Jérémy Chardy before losing to eventual champion Novak Djokovic in five sets.

Seeded 14th at the US Open, Čilić defeated Marcos Baghdatis, Illya Marchenko and Kevin Anderson to set up a fourth-round fixture against Gilles Simon, beating the Frenchman for the first time in five matches.

After a 2:2 tie between two countries, however, Čilić stepped up and played the deciding fifth singles rubber in place of young compatriot Borna Ćorić, where he defeated Thiemo de Bakker.

On 18 October, it was announced Čilić, as the then reigning US Open champion, had become the fifth player (after Djokovic, Nadal, Federer and Wawrinka) to qualify for the ATP World Tour Finals in London from 9–16 November.

[35] Čilić subsequently withdrew from the Valencia Open and Paris Masters in order to allow time for an arm injury to heal before the tour finals.

Čilić returned to Flushing Meadows for the US Open to defend his title, reaching the semi-finals where he was beaten in straight sets by Novak Djokovic who also went on to win in the final.

At the Wimbledon Championships, Čilić repeated his efforts of the previous two years making the quarterfinals, after eliminating rival Kei Nishikori in the fourth round.

The Croat beat Viktor Troicki, Fernando Verdasco, Tomáš Berdych, Borna Ćorić and Grigor Dimitrov in the route to the final.

The match garnered minor criticism from some tennis pundits for being played indoors to favour Federer, despite the Australian Open traditionally being an outdoor event.

In the first two Masters 1000 events of the season Čilić was defeated by Philipp Kohlschreiber (at Indian Wells, in the round of 32) and John Isner, the eventual champion of Miami.

As a result of his poor form in the early hard court season, Čilić fell from the worlds top ten for the first time in over two years.

After another two winless tournaments to start the clay court season (at Monte-Carlo and Budapest), Čilić finally broke his slump at the Madrid Masters by winning three consecutive matches against Martin Kližan, Jan-Lennard Struff, & Laslo Djere on the way to the quarterfinals.

Čilić started the 2020 season at the Australian Open where he beat Corentin Moutet, Benoît Paire, and Roberto Bautista Agut before losing to Milos Raonic in straight sets.

In June, Čilić won the Stuttgart Open, defeating third seed Félix Auger-Aliassime in the final in straight sets to win his 19th singles title and first in three years.

[55][56] The following week, Čilić won the St. Petersburg Open, defeating fifth seed Taylor Fritz in a three-sets final to win his 20th singles title.

[57] On the way to the title, he also defeated Albert Ramos Viñolas, Karen Khachanov, Roberto Bautista Agut and Botic van de Zandschulp.

777, Čilić reached the semifinals at the Hangzhou Open as a wildcard with wins over two Japanese players, eighth seed Yoshihito Nishioka[72] and qualifier Yasutaka Uchiyama, saving two match points against the latter.