This study was aimed at comparing the effectiveness and efficiency of direct instruction and problem solving approaches in teaching social skills to children with mental retardation. The design was adapted alternating treatment design. The subjects of the study consist of a girl and a boy between the ages of 11 and 13 who are mentally retarded. In order to collect the research data, teacher's interview form, the control check lists of social skills, criterion-referenced tests and data record sheets to use during direct instruction and problem solving approaches, efficiency form were developed and used. Visual graphical analysis method was used in the analysis of the data. The outcome shows that direct instruction approach was more effective than problem solving approach in teaching social skills to first subject. In acquisition of social skills direct instruction was more efficient in terms of total training time and training errors through criterion than problem solving approach.