Implicit theories about the nature of human attributes as either malleable or fixed influence how people perceive knowledge and approach different tasks. Two studies explored the relationship between implicit theory of writing ability, metacognitive strategy knowledge (MSK), and strategy use in the context of academic writing. The pre-study with N = 51 university students revealed a significant correlation between students’ implicit theories and their MSK. Self-reported quality and diversity of strategy use, assessed by open-ended questions, were not significantly associated with students’ implicit theories. Expanding strategy use measures, study 2 (N = 133) found significant correlations between a more malleable theory and more frequent use of metacognitive strategies. Confirming the results of the pre-study, the results of study 2 showed that a more malleable theory of writing ability was directly associated with higher MSK. In sum, the results illustrate the importance of linking implicit theories to self-regulated learning.