This study investigated the relationships between foreign language learners’ self-beliefs conceptualized as self-confidence and self-efficacy, motivation, and antecedents of their self-beliefs, namely, social comparison and temporal comparison. Using data collected through a questionnaire involving 284 female university students learning English in Japan, this study attempted to construct a model explaining the relationships between the variables through the use of structural equation modeling. The results indicated the following possibilities: (1) self-efficacy influenced self-confidence; (2) both self-confidence and self-efficacy led to more self-determined forms of motivation, which resulted in motivated learning behavior; and (3) social comparison and temporal comparison affected the two self-beliefs, especially the former on self-confidence and the latter on self-efficacy. These findings suggested a close link between self-confidence and self-efficacy, a powerful influence of these self-beliefs on motivation and motivated learning behavior, and different functions that social and temporal comparisons play in the formation of self-confidence and self-efficacy among foreign language learners.