In this report, coparenting behaviors during triangular interactions among families raising a 3-month-old infant in Turkey are examined. Given the significant role played by extended family members in Turkish culture, coparenting dynamics were examined as mothers and babies played together with grandmothers, as well as together with fathers. Forty-five families took part, and 42 father–mother–baby and 33 grandmother–mother–baby triangular interactions of approximately 10 min in length were filmed during the Lausanne Trilogue Play. From videotapes of the interactions, individual and mutual coparenting behaviors were evaluated using the Coparenting and Family Rating System: 3 Month Adaptation (CFRS3M). Results indicated that while mothers’ own parenting behavior when in the LTP role of Active Parent (AP) was comparable whether with fathers or grandmothers, their behavior when in the LTP role of third party parent (TPP) was comparatively more engaged while with fathers than while with grandmothers. Fathers were comparatively less engaged when occupying the TPP role than were mothers in the TPP role, while grandmothers showed more flirting and distracting behavior in the TPP role than did either fathers or mothers. These findings are significant in documenting meaningful distinctions in Turkish grandmothers’ as well as in Turkish fathers’ and mothers’ coparenting propensities when engaging in triangular interactions with babies during the LTP.