Self-construal refers to the process by which individuals define the self in relation to others. It underpins cognition, motivation, and social behavior. While the importance of the self is well acknowledged in the field of second language (L2) learning motivation, how self-construal is associated with L2 learning motivation in project-based learning (PBL) settings remains understudied. Further, considering the observed link between self-construal and gender, self-construal may also account for how gender differences emerge in L2 learning motivation. This study examined the associations among self-construal, gender, and motivation to learn English as a foreign language (EFL) in a PBL context. Japanese university students responded to questionnaires on self-construal and motivation after being taught by the PBL approach for one year. The results showed a prominent impact of gender and self-construal on motivation. Female students and students with higher interdependent self-construal tended to be more motivated toward L2 learning, while male students and students with lower interdependent self-construal tended to be less motivated.