The psychological well-being of primary school students holds significant value for their academic success and overall life development. A growth mindset is one of the critical factors influencing psychological well-being, yet the mechanisms through which a growth mindset exerts its impact remain underexplored. This study investigates the relationship between growth mindset and psychological well-being, focusing on the mediating role of grit and academic self-efficacy among primary school students. A sample of 301 students from a primary school in Northeast China was selected via convenience sampling. Data were collected using validated questionnaires and analyzed using SPSS 26.0. Serial mediation analysis was performed with Hayes' PROCESS macro (Model 6, V4.0). Results indicated that growth mindset indirectly predicted psychological well-being through grit and academic self-efficacy. Both constructs served as individual mediators and acted as serial mediators in the pathway from growth mindset to psychological well-being, fully bridging the connection. These findings suggest that fostering a growth mindset, along with grit and academic self-efficacy, can enhance psychological well-being among primary school students. Educators and policymakers are encouraged to implement interventions targeting these factors to support students' overall development.