This study examined the effect of a mother–baby intervention on the quality of mother–child interaction, infant–mother attachment security, and infant socioemotional functioning in a group of depressed mothers with infants aged 1–12 months. A randomized controlled trial compared an experimental group (n = 35) receiving the intervention (8–10 home visits) with a control group (n = 36) receiving parenting support by telephone. There were assessments pre, post, and follow-up after 6 months. The intervention had positive effects on the quality of mother–infant interaction. Infants in the experimental group had higher scores for attachment security and for one aspect of socioemotional functioning, namely, competence. The intervention proved successful in preventing deterioration of the quality of mother–child interaction.