This study interrogates the association of parenting style with adolescents' physical activity (PA) motivation while accounting for specific parental PA practices (i.e., monitoring, encouragement, and modeling) as a mediating mechanism in this context. The sample comprised 143 adolescent boys (Mage = 14.43, SD = 1.60) and 165 adolescent girls (Mage = 14.13, SD = 1.66), who participated in an online survey. Participants were asked to complete various questionnaires, which include the Self-Motivation Inventory for Children, the Parental Authority Questionnaire, and several scales of parental PA-related practices. Boys reported significantly higher parental PA-related practices and higher PA motivation than girls. Path models used to test research hypotheses indicated that authoritative parenting was indirectly associated with adolescents' PA self-motivation through parental PA-related practices as mediators, whereas paternal authoritarian parenting had a similar but smaller positive effect on boys' PA motivation. The indirect association of paternal authoritative parenting with adolescents' PA motivation through PA-related practices was stronger for girls than for boys, suggesting that an authoritative fatherhood climate is more influential on girls' PA motivation. Consistent with the reciprocal role theory, our observations suggest that fathers' parenting, rather than mothers' parenting, tends to discern more between boys and girls in advocating child's PA. The study's conclusions and practical implications are discussed in terms of sex-based variations in parental influence.