Background: The Picture Exchange Communication System (PECS) is a popular augmentative communication system frequently used with "nonverbal" children with autism. Several studies suggested that PECS could represent an effective tool for promoting improvement of several social-communicative skills. Only sparse evidence is instead available on the long-term effectiveness of this treatment system. Aims: To test the long-term effects of PECS, for which a follow-up study was conducted by assessing social-communicative skills in nonverbal preschool children with autism after 12 months from treatment completion. Methods & Procedures: Two groups of children (N = 14) were assessed; one group had completed the PECS training and the other conventional language therapy (CLT). At follow-up all children received the same pre- and post-treatment assessment. Outcome measures were the following: Communication and Social domains of Autism Diagnostic Observation Schedule (ADOS); Language and Personal-Social subscales of the Griffiths' Mental Developmental Scales (GMDS); Communication and Social Abilities domains of the Vineland Adaptive Behavior Scales (VABS); and several social-communicative variables coded in an unstructured setting. Outcomes & Results: The PECS group showed significant improvements compared with the CLT group on ADOS severity scores (Communication, Social and Total), on GMDS Social domain and on VABS Communication and Social domains. PECS-related gains on the VABS Social domain and on specific social-communicative measures coded during free-play, i.e. frequency of joint attention and initiation, and duration of cooperative play, were stable after 1-year follow-up. Cooperative play continued to improve on follow-up with respect to both post- and pre-treatment assessment. Conclusions & Implications: These findings demonstrated that PECS training can promote long-term enhancement of specific socio-communicative skills in children with autism.