The present study investigated how self-related English learning motivation among Taiwanese adolescent learners differs between students who only receive English instruction in formal schooling and those who have additional private tutoring. A total of 1,698 teenage English learners in public secondary schools across Taiwan completed a self-reported questionnaire based on the L2 motivational self-system theory (Dörnyei, 2005, 2009). The results showed that students who had additional tutoring had a significantly stronger intention to learn English and exhibited a higher frequency of English learning behaviors compared with those who only received English instruction in the mainstream. Regression analyses revealed similarities and differences between the motivational profiles and self-conceptualizations of those with and without private tutoring, revealing that ought-to self, learning attitudes, and learning experiences were prominent predictors of learning motivation for both groups. For students without tutoring, the influence of prevention-based instrumentality was found in their intention to invest effort and their perceived motivated learning behaviors. While the motivational power of ought-to self was observed in both groups, ideal self was only a pertinent contributory factor of intended effort in those who had tutoring. The study highlights the importance of considering learning experiences across diverse learning contexts in L2 motivation research.