<p>Rates of U.S. adolescent sexually transmitted infections and unintended pregnancies are alarmingly high, highlighting the importance of parent-adolescent sexual communication (PASC). However, parents frequently cite the lack of knowledge/confidence as barriers to meaningful PASC. This research explored these barriers via a novel application of the Implicit Theories framework, Implicit Theories of Sexual Knowledge (ITSK). ITSK is defined as the extent to which individuals believe that sexual knowledge is innate (entity) or learned (incremental). In particular, the ITSK framework was applied to predict parents’ frequency of PASC, comfort during PASC, and the breadth of topics covered via a correlational and experimental study. For Study One, 331 parents completed the ITSK scale and questionnaires assessing frequency, comfort, and breadth of PASC. For Study Two, 176 parents received one of three fictitious <i>Psychology Today</i> articles priming incremental beliefs, entity beliefs, or serving as a control. After receiving the manipulation, parents received modified questionnaires assessing anticipated frequency, comfort, and breadth of PASC. The results from Study One indicated that incremental theorists engaged in more frequent PASC and discussed a larger number of topics with their children than did entity theorists. In Study Two, those receiving the incremental prime anticipated sharing a greater number of topics with their children than did those receiving the entity prime. These results suggest that parents’ beliefs regarding the malleability of sexual knowledge affect the breadth of information shared with their children. Implications for educators, including the importance of embedding ITSK-based information in sexual health educator training, are discussed.</p>