Transactive memory refers to the way people in close relationships use each other’s memories as extensions of their own to improve their collaborative performance. Although pioneer research has been conducted among close couples, no studies have examined the effects of the cultural composition of couples on transactive memory. The goal of this study was to extend research about the positive impact of cultural diversity on team performance to mixed- (French–Moroccan) and same-culture couples (French–French, Moroccan–Moroccan). Thirty heterosexual couples aged from 22 to 55 years (M = 42.25 years and SD = 8.15) performed a culture-based memory game with cards depicting French and Moroccan culture. The order in which the pairs of cards was found is thought to reflect the efficiency of transactive memory. Results revealed that collective performance was better in mixed French–Moroccan couples than in same-culture couples but only for the French culture cards. These findings suggest that cultural diversity in couples has an impact on transactive memory and should be taken into consideration.