Two studies explored the role of parents’ unconditional positive regard (UCPR) as perceived by adolescents and young adults in promoting the effectiveness of specific parenting practices that may support offspring's academic autonomous motivation. Study 1 tested the hypothesis that UCPR predicts rationale-giving and choice-provision practices and, at the same time, moderates their relations with adolescents’ autonomous motivation. Study 2 replicated the association between UCPR and the parental practices, and further explored the role of parents’ authenticity as an antecedent of UCPR and parental autonomy support. Study 1 included 125 adolescents and Study 2 considered 128 college-students and their mothers. The offspring reported on their perceptions of their mothers and on their autonomous motivation, and the mothers reported on their sense of authenticity. Both studies found consistent associations between UCPR and parenting practices that may support autonomous motivation. Moreover, Study 1 demonstrated that the rationale giving and choice provision were more strongly related to adolescents’ autonomous motivation when adolescents perceived mothers as high on UCPR. Finally, Study 2 demonstrated that mothers’ authenticity predicted UCPR, which in turn was related to autonomy-supportive parenting. Findings support the assumption that parents’ autonomy-supportive practices are more effective when accompanied by UCPR.