The aims of the present study were to validate the Norwegian translated Muscle Dysmorphic Disorder Inventory (MDDI) and explore the presence of muscle dysmorphia (MD) symptomatology in Norwegian gym-going men. A secondary aim was to examine differences in MD symptomatology and weekly training duration (WTD) according to the participants’ body mass index (BMI), and further investigate relationships between all measured variables. Participants (N = 124; Mage = 24.8, SD = 6.7 years) completed the translated MDDI, and according to BMI, 65 participants were of normal weight and 59 were overweight. A good fit from the confirmatory factor analysis, the results from the construct validity from the principal components analysis, and the detected good internal consistency indicate that the Norwegian translated MDDI is a valid and reliable measure for MD symptomatology. Moreover, MD symptomatology was present with mean scores of 33.7 (SD = 6.6), 15.2 (SD = 3.9), 10.4 (SD = 3.5), and 8.1 (SD = 2.6) for the MDDI total, and for the subscales drive for size (DFS), functional impairment (FI), and appearance intolerance (AI), respectively. Statistical significant differences were detected between the normal weight and overweight participants in DFS, AI, FI (d≤.4, p<.01) and in WTD (d=.7, p<.01), but not significant for the MDDI total score (d=.1, p>.05). Lastly, WTD had a statistically significant correlation with FI and BMI (p<.01); whereas BMI had a statistical significant correlation with DFS, FI, and AI (p<.05). In conclusion, the translated Norwegian MDDI was found to be valid, but additional validations are needed with larger sample sizes. The presence of MD symptomatology and WTD was higher in the overweight compared to the normal weight participants. The findings further suggest that the subscale scores might better assist practitioners in evaluating MD concerns and offer appropriate care, as a MDDI cut-off score have yet to be validated.