According to the Social Cognitive Theory and the perspectives of parental differential treatment, the current research proposed and verified a moderated mediation model to explore the mediating role of teacher support and the moderating role of only-child (OC) /non-only-child (NOC) status in the relationship between hardiness and college student learning adaptation. A questionnaire survey of 1138 Chinese college students was conducted using the hardiness scale, the learning adaptation scale, and the student perception of teacher supportive behavior questionnaire. The results revealed a significant positive effect of hardiness on college student learning adaptation. The mediation model analysis showed that teacher support had a complementary partial mediating role in the relationship between hardiness and college students’ learning adaptation. Furthermore, the moderated mediation model analysis suggested that OC/NOC status moderated the second half of this mediating relationship and indicated that teacher support had a stronger effect on the learning adaptation of college students with OC status than NOC status. The research results not only enrich our understanding of the internal influence mechanism of the relationship between hardiness and college students’ learning adaptation, but also broaden the research on the identity difference between OC/NOC status. Practical discussions and suggestions are proposed based on the results.