On 23 July 2019, Fekir signed for Spanish club Real Betis as part of the deal which also saw his brother Nabil Fekir move to Betis. Lyon will reserve 50% of any future sale of Yassin as well.[5] He was initially assigned to the B-team in Tercera División, and on the last day of transfer window, he was loaned out for the season to CD Guijuelo of Segunda División B.[6]
Fekir was promoted to the Betis first team squad on 1 February 2021, and registered for the rest of the La Liga season.[7] On 31 August, he was demoted back to the B-team for the 2021–22 Primera División RFEF.