Australian Open mixed doubles event partnering Barbora Krejčíková. He also reached the doubles final at the 2020 US Open partnering again with Wesley Koolhof. As a result he finished the year at No. 8 in the top 10 rankings in doubles and No. 3 in the doubles race with his partner Wesley Koolhof. 2021: New partnership, eight ATP titles including a historic Wimbledon title, First Croatian Olympic tennis champion, World No. 1 Starting 2021, Mektić partnered successfully with his compatriot Mate Pavić. They won four ATP titles including the doubles title at the 2021 Miami Open in the beginning of April and reached the 2021 Australian Open doubles semifinals and 2021 Dubai Tennis Championships final in the first three months of the year. Following these results, Mektić returned to his No. 4 high-career ranking on April 5. On April 18, Mektić clinched his fifth ATP Masters 1000 in a row and second Masters title of the year at the 2021 Monte-Carlo Masters where the pair defeated, for the second time in the final of a Masters in 2021, the British pair of Neal Skupski and Dan Evans. Seeded No. 2 the pair also reached the final at the 2021 Mutua Madrid Open Masters where they lost to the No. 3 seeded pair Horacio Zeballos and Marcel Granollers and the final of the Italian Open where they won the title defeating No. 5 seeded pair Rajeev Ram and Joe Salisbury. After the win, Mektić moved to his career-high ranking of World No. 2 on 17 May 2021. In their first Grand Slam doubles final, top seeds Mektić and Pavić had the biggest victory of their 2021 season as a team defeating Granollers and Zeballos to triumph in doubles at the 2021 Wimbledon Championships. They became the first Croatian players to win the Wimbledon men's doubles title. They are also the first players from their country to win at the All England Club since Goran Ivanisevic's 2001 victory in singles and Ivan Dodig's 2019 mixed doubles win with Latisha Chan. At the Olympics he won the gold medal with Pavić in an all-Croatian final defeating Ivan Dodig and Marin Cilic. It was the country's first gold medal in the sport and the third time in the Olympics men's doubles' history that the same country won both gold and silver, and the first one since 1908. On 18 October 2021, following a quarterfinal