Recent studies show the importance of the father’s presence on the family’s mental health, affecting, among others, on the mother-child bond. Considering this information, the present study does a comparative analysis of the quality of mother-child interaction on dyads of nuclear and single-mother, Chilean, low-income families. 80 Dyads were studied, 40 belonging to single-mother families and 40 to nuclear families. The children’s ages were between 4 and 17 months (M = 12.36, SD = 3.2) and the mothers between 15 and 44 years old (M = 26.74, SD = 7.53). The mother’s sensitivity answer and the quality of the interaction were evaluated with the CARE-Index (Crittenden, 1997) instrument. The results show a greater interaction quality among nuclear families, with important differences and medium effect sizes on the cognitive aspects of the interaction.