This report examines coparenting and triadic interactions in 19 unmarried, first-time African American families as fathers, mothers, and 3-month-old infants navigated the Lausanne Trilogue Play (LTP; E. Fivaz-Depeursinge & A. Corboz-Warnery, 1999). Parents in 10 of the 19 families reported coresidence at the time of the 3-month assessment, and the other 9 sets of coparents lived apart. All participating families had taken part in a prenatal intervention emphasizing the importance of father engagement in children’s lives, and in all families, parents reported episodic to regular father contact with the children at 3 months. Analyses of LTP sessions revealed that 9 of the 19 families exhibited high levels of coparenting solidarity—cooperation and family warmth accompanied by low levels of coparenting competition and disengagement. Among the remaining 10 families, competitiveness (verbal sparring, interference) and/or disengagement (repeated, episodic absenting by one or both parents from the ongoing interaction) signaled strain and challenges to solidarity. Differences between the higher and lower solidarity groups were found in father-reported relationship rapport. However, coresidentiality versus noncoresidentiality of the parents did not distinguish high- from low-solidarity groups. A case analysis of one family’s triadic session is presented to elucidate the rich potential for clinical intervention in triadic work with fragile family systems. Implications of the study and its findings for theory, research, and clinical work with unmarried fathers and families, along with limits of the study design and generalizability of findings, are discussed.