According to Bandura's theory of reciprocal determinism, self-efficacy and academic achievement can have a mutual influence over one another. While empirical research generally supports this position, little focus has been given to within- and between-person factors that may moderate this relationship. The present study explored how initial performance and task difficulty impact learners' performance and self-efficacy trajectory over subsequent tasks. A diverse university sample of 261 students; 118 females aged 18-67 and 143 males, aged 18-64, was used. Significant positive pathways were found in the achievement-self-efficacy direction, but not for pathways in the self-efficacy-performance direction, failing to support the reciprocal hypothesis. Repeated measures ANOVA also revealed a moderating influence of initial task performance on the interaction between task difficulty and achievement over time. The findings highlight the importance of enhancing academic performance through scaffolded mastery, particularly for those with initial low performance outcomes, to build self-efficacy for learnt skills.