Background <p>Previous studies on patients with diabetes have reported that weight stigma is associated with overeating and poor dietary self-control. Moreover, reports examining the associations between weight stigma and decreased dietary diversity in patients with diabetes do not exist. Therefore, we examined the relationship between weight stigma and dietary diversity in this patient population.</p> Methods <p>In this study, the dietary diversity in patients with diabetes receiving outpatient treatment at Ise Red Cross Hospital were measure using Food Frequency Score (FFS) and Protein Food Frequency Score (PFFS). The Japanese version of the Weight Self-Stigma Questionnaire (WSSQ-J) was used to measure weight stigma. Using multiple regression analysis with FFS and PFFS as dependent variables and WSSQ-J scores (WSSQ-J total, self-devaluation subscale and fear of enacted subscale scores) as explanatory variables, standardized partial regression coefficients (β) for weight stigma and dietary diversity were calculated based on sex and age.</p> Results <p>A total of 315 patients (178 men and 137 women) were included in the analysis. The adjusted β for FFS of the fear of enacted subscale scores in women and older adults were − 0.209 (<i>P</i> = 0.026) and − 0.157 (<i>P</i> = 0.040), respectively. Furthermore, the adjusted β for the PFFS of the fear of enacted subscale scores in women and older adults were − 0.216 (<i>P</i> = 0.026) and − 0.191 (<i>P</i> = 0.014), respectively. There was no relationship with FFS and PFFS for WSSQ-J total scores, self-devaluation subscale scores or fear of enacted subscale scores in men and younger participants aged &lt; 65 years.</p> Conclusions <p>The results of the present study revealed that weight stigma (fear or embarrassment about being stigmatized because of weight) was associated with reduced dietary diversity among women and the older adults with diabetes.</p>