See main article: 2021 Kremlin Cup. Shuko Aoyama and Ena Shibahara were the defending champions, having won the previous event in 2019,[1] but chose not to participate.
Jeļena Ostapenko and Kateřina Siniaková won the title, defeating Nadiia Kichenok and Raluca Olaru in the final, 6–2, 4–6, [10–8]. Ostapenko and Siniaková won the title after saving three match points in their quarterfinal match against Viktória Kužmová and Alexandra Panova. This was the first time that Siniaková won a doubles title without regular partner Barbora Krejčíková since January 2019.[2]