The aim of the study is to examine effects of a program for enhancing infant with developmental delay and mother, parenting efficacy. The subject of this study were 3 pairs of infant with developmental delay and their mothers at A therapy center in D city. Mother-child group play therapy conducted once a week, total 12 sessions and each session was conducted for 50minutes. The result of this study are as follows. First, infant with developmental delay interaction behavior showed that the persistance, cooperative, joint attention, interest were increased than before. Mother’s interaction behavior showed that verbal praise, acceptance, enjoyment increased, while the directivity achievement were decreased. Second, mother’s parenting efficacy showed that cognitive parenting efficacy was increased and emotional parenting efficacy was maintained or increased. Therefore, The mother-child group play therapy positively changed the interaction behavior infant with developmental delay and mother’s, parenting efficacy.