Abstarct: Background & Objectives: In the sport of bodybuilding, accurate nutritional knowledge can play a pivotal role in enhancing performance, improving muscular strength, and optimizing body composition. Nevertheless, the levels of nutritional knowledge among bodybuilders and their relationships with strength indices and biometric markers remain scarcely examined in many regions of the country. This study aimed to assess the nutritional knowledge status of bodybuilders in Semnan and evaluate its relationship with performance in strength movements and anthropometric variables. Materials & Methods: This descxriptive–analytical study was conducted among active bodybuilders in Semnan. A total of 155 individuals meeting inclusion criteria (at least 6 months of training history, good health, informed consent) were selected. Those with specific medical conditions or controlled use of hormones/supplements were excluded. Nutritional knowledge was measured via a validated questionnaire covering macronutrient requirements, meal timing, supplements, and sports nutrition principles. Strength tests were carried out using one-repetition maximum (1RM) assessments in three movements: bench press, overhead press, and squat. Body variables including weight, arm circumference, and waist-to-hip ratio were measured. Demographic data and supplement/hormone use were self-reported via forms. Data were analyzed in SPSS: descxriptive statistics (mean, percentage, standard deviation) were first computed, followed by Spearman correlation for relationships, independent t-test or Mann–Whitney U for two-group comparisons, and ANOVA for multiple group comparisons. The significance level was set at 0.05, and in crosstab tables observed and expected percentages and standardized residuals were examined. Results: Findings revealed that most bodybuilders had a moderate level of nutritional knowledge and none achieved the “excellent” category. Nutritional knowledge was significantly and positively correlated with strength performance in the tested movements; however, it was not significantly associated with waist-to-hip ratio or arm circumference. No meaningful association was found between nutritional knowledge and supplement use or hormone status in this sample. In demographic comparisons, a significant difference was observed between males and females in nutritional knowledge, but age had no significant effect. Conclusion: While nutritional knowledge may contribute to improved strength performance, mere awareness is insufficient. There is a clear need for educational interventions, practical nutrition programs, and culture-building among bodybuilders. Future studies are recommended to implement practical interventions and examine mediator variables such as diet quality, meal timing, and sources of nutritional information.