Marie Kaldvee/Harri Lill (Tallinn, EST) qualified for the 2021 Oberstdorf International Mixed Doubles Cup playoffs, dropping their quarterfinals match 8-4 against Johanna Heldin/Daniel Magnusson (Uppsala, SWE). of the 2021 Oberstdorf International Mixed Doubles Cup in Oberstdorf, Germany;
 
Kaldvee/Lill finished 3-2 in the 16-team qualifying round. . In their opening game, Kaldvee/Lill lost 9-7 to Katja Schlegel/Sebastian Keiser (Zug, SUI), then responded with a 9-4 win over Martina Fenykova/Martin Votava (Prague, CZE). Kaldvee/Lill won 10-9 against Daniela Rupp/Kevin Wunderlin (Zug, SUI). Kaldvee/Lill went on to lose 7-3 against Adela Walczak/Andrzej Augustyniak (Lodz, POL). Kaldvee/Lill responded with a 7-5 win over Martine Ronning/Mathias Braenden (Lillehammer, NOR) in their final qualifying round match.
 
. For week 6 of the event schedule, Kaldvee/Lill did not improve upon their best events, remaining at 778th place on the World Ranking Standings with 86.821 total points. Kaldvee/Lill ranks 308th overall on the Year-to-Date rankings with 0.000 points earned so far this season.