The Autism spectrum disorder severely impairs communication and social skills. The aim of the present study was to examine the effects of two interventions—Picture Exchange Communication System (PECS) and speech training—on the development of communication and social skills in nonverbal children with autism, and to compare the effectiveness of these two methods. This study was applied research conducted in a quasi-experimental design. The target population consisted of nonverbal children with autism spectrum disorder at level three. Twelve children (three girls and nine boys) were randomly assigned into two groups of six participants each. A pretest–posttest design without a control group was employed, and the Gilliam Autism Rating Scale–Third Edition (GARS-3) was used as the assessment tool. Both PECS and speech training interventions were implemented over 18 sessions. Data were analyzed using univariate and multivariate covariance analyses. The paired t-test results indicated that the scores of participants in both the PECS and speech training groups decreased significantly (p < 0.05), demonstrating the effectiveness of the interventions in improving communication and social skills in the target group. Finally, the effects of PECS and speech training were compared, and the results revealed a significant difference between the two groups (p < 0.05). Findings indicated that both interventions were effective in enhancing communication and social skills; however, the impact of PECS was greater and statistically more significant.