We tested the interaction between task value and self-efficacy on defensive pessimism, academic cheating, procrastination and self-handicapping among 574 Korean 11th graders in the context of English as a foreign language. We hypothesised that perceiving high value in tasks or domains for which self-efficacy was low would pose a threat to perceived self-worth, leading students to resort to various maladaptive achievement strategies. Hierarchical multiple regression analyses demonstrated that, consistent with our hypothesis, the relationships of task value with academic cheating and procrastination depended on the level of self-efficacy. Perceiving high intrinsic value positively predicted academic cheating for students with low self-efficacy but not for students with high self-efficacy. Likewise, perceiving intrinsic or utility value positively predicted procrastination for students with low self-efficacy but not for students with high self-efficacy. Our findings support the major tenets of self-worth theory.