[citation needed] After spending a better part of a decade on the ATP challenger tour and achieving a career high ranking of No.

The same year he reached his first ATP men's doubles final as a wildcard at the 2016 Croatia Open Umag with his compatriot Antonio Šančić.

The same year Mektić reached his first Grand Slam finals (in mixed doubles) at the 2018 US Open, partnering Alicja Rosolska, and won the Davis Cup playing for Croatia.

3 seeded pair Horacio Zeballos and Marcel Granollers[5] and the final of the Italian Open where they won the title defeating No.

[7] At the Olympics he won the gold medal with Pavić in an all-Croatian final defeating Ivan Dodig and Marin Cilic.

[12] At the ATP 500 2022 Queen's Club Championships Mektic won his third title for the season with Pavic and twentieth overall in his career.

[19] After reuniting with Wesley Koolhof for the 2024 season, he won his fourth ATP 500 title at the 2024 ABN AMRO Open in Rotterdam, his second at this tournament.

Unseeded, he won the 2024 BNP Paribas Open with Wesley Koolhof defeating Marcel Granollers and Horacio Zeballos in the final.

[20][21] Also unseeded at the 2024 Rolex Shanghai Masters, they reached the semifinals defeating Nathaniel Lammons and Jackson Withrow and kept their position of No.

[22] Following reaching the final with a win over Santiago González and Édouard Roger-Vasselin, the duo Mektić and Koolhof climbed a position up to No.

They won their fourth title for the season defeating Argentinian duo of Máximo González and Andrés Molteni.

[23] Mektić and Koolhof won their fifth title of the season at the Paris Masters, defeating Lloyd Glasspool and Adam Pavlásek in the final which went to a deciding champions tiebreak.