This research investigates the evidence demonstrating the reliability and convergent validity between the Social Skills Inventory for Adolescents and the Matson Evaluation of Social Skills with Youngsters in two groups: the first with 136 adolescents from a public school (89 females and 47 males, with ages ranging from 12 to 17 years, 13.98 ± 1.24 years); the second with 24 adolescents from a socio-educational program (ages ranging from 13 to 17 years, 15.64 ± 1.18 years). The results showed low and moderate correlations between some subscales of both instruments (Matson Evaluation of Social Skills with Youngsters and Social Skills Inventory for Adolescents), evidencing convergent validity between the Social Skills Inventory for Adolescents scores and the social skills/assertiveness" subscale of the Matson Evaluation of Social Skills with Youngsters. Comparisons between the groups indicated that the second sample had less difficulty in Civility (Social Skills Inventory for Adolescents) than the first sample (public school adolescents).