[2][3] Galán made his ATP main draw singles debut at the 2015 Claro Open Colombia where he was given a wildcard.

[6] As a result of his first and best Masters 1000 third round showing thus far at the 2021 Miami Open, defeating 15th seed Alex de Minaur en route,[7] and then losing to Lorenzo Sonego,[8] he reached a career-high of World No.

At the 2022 Córdoba Open he reached his first ATP quarterfinal of the year as a lucky loser where he lost to top seed Diego Schwartzman.

After missing three major events, he returned to the 2022 Wimbledon Championships where he reached the second round for a second consecutive year defeating Dominik Koepfer.

He moved to the third round for the first time at this Major after the withdrawal of 17th seed Roberto Bautista Agut due to a positive COVID-19 test.

5 Stefanos Tsitsipas to advance to the second round, recording his first victory over a Top-5 player and for Colombia since Iván Molina took down then-No.

[19] At the 2023 Mutua Madrid Open in the first round, he played in the longest tiebreak of the ATP season thus far, falling 17-15 in 25-minutes to Alexander Bublik.

[22] At the 2024 Australian Open, Galan needed almost five hours to the minute to win his first round match at this Major over local wildcard Jason Kubler.

[24] In January 2025, at the Punta del Este Open in Uruguay, Galan claimed his fifth Challenger title and first since April 2022.