Considerable research suggests a link between mind wandering and diminished levels of motivation and interest. During episodes of mind wandering, individuals may engage in efforts to redirect their attention back to the task at hand (known as focus back effort). Building on the resource-control hypothesis, we hypothesized that the influence of interest and motivation on mind wandering may be mediated by focus back effort. In Study 1, we employed a latent-variable approach to investigate these relationships across three tasks with varying cognitive demands. The results showed that individual differences in interest indirectly influenced mind wandering through the mediating factors of motivation and focus back effort. Furthermore, individual differences in interest indirectly predicted task performance through the mediating factors of motivation, focus back effort, and mind wandering during the high-load task. In Study 2, we replicated the relationships among these factors in a reading comprehension task. The results consistently support the role of focus back effort as an adaptive mechanism for executive control, enabling the allocation of cognitive resources to both mind wandering and task performance. These findings underscore the significance of focus back effort in elucidating the interplay between mind wandering, motivation, interest, and task performance. Importantly, our results align with the resource-control theory.