Background: Lynch Syndrome (LS) mutation carriers are at high risk for various cancer types, particularly colorectal cancer. Adherence to lifestyle and body weight recommendations for cancer prevention may lower this risk. To promote adherence to these recommendations, knowledge on determinants of adherence in LS mutation carriers is needed. Therefore, this study aimed to identify determinants of adherence to lifestyle recommendations for cancer prevention in LS mutation carriers. Methods: Five focus groups were conducted with DNA confirmed LS mutation carriers (n = 29). Transcripts were analyzed by thematic analysis, using the Health Belief Model (HBM) as a theoretical framework. Results: Tolerance of an unhealthy lifestyle because of the desire to enjoy life and avoidance of LS dominating their life were most frequently reported as important barriers of adherence to the recommendations. Most important facilitators of adherence to the recommendations were enhancement of wellbeing and intolerance of unhealthy foods due to colon surgery. Conclusions: This study provided a comprehensive overview of determinants of adherence to recommendations for cancer prevention. These determinants, of which some are typically and unique for LS mutation carriers, can be used to design a lifestyle intervention that meets the needs of LS mutation carriers.