Ymer made his ATP main draw singles debut at the 2013 Swedish Open where he lost in the first round to Grigor Dimitrov.

[6] At the 2015 Barcelona Open Banc Sabadell, Ymer defeated Thiemo de Bakker and Nick Kyrgios to reach the third round, where he lost to David Ferrer.

Ymer won his first ATP Challenger title at the 2015 Città di Caltanissetta, beating American Bjorn Fratangelo in straight sets.

[7] Ymer qualified to the main draw of 2015 Wimbledon Championships after wins against Thomas Fabbiano, Boy Westerhof and Guido Pella.

[10] There he won his first Grand Slam main draw match, beating Dudi Sela in straight sets.

15 Aslan Karatsev in straight sets in second round of 2022 Maharashtra Open for his first top-20 win in his career to reach the quarterfinal, only his second since Gstaad in 2016.

At the 2023 Stockholm Open he reached the quarterfinals as a wildcard defeating Roberto Bautista Agut and qualifier Dino Prizmic.