Full text Article. Also available at https://doi.org/10.1371/journal.pone.0244813The prevalence of overweight and obesity is rising at a rapid pace and is associated with negative health consequences like cardiovascular diseases, type 2 diabetes and cancer. Obesity is a multifactorial problem that develops mainly from lifestyle factors including physical inactivity and poor dietary intake. Dietary diversity is a simplified method for assessing the adequacy and quality of diet and is associated with nutritional need and overall health status. Therefore, we conducted this study to synthesize the associations between consumption of a diversified diet and overweight/ obesity among adults living in pastoral communities in Monduli district in Tanzania. This was a cross-sectional study conducted among 510 adults aged ≥ 18 years old in the Monduli district, Arusha region in Tanzania. We conducted face-to-face interviews to collect information about socio-demographic characteristics, 24-hours dietary recall, and anthropometric measurements. The dietary diversity score (DDS) was constructed and used to determine the diversity of the diet consumed. We performed the multivariate Poisson regressions to determine the prevalence ratio (PR) with 95% confidence intervals (CI). The dependent variables were overweight and general obesity as measured by body mass index (BMI), abdominal obesity measured by waist-hip ratio (WHR) and waist circumference (WC). The prevalence of general obesity based on BMI was 20.2% (95%CI; 16.9–23.9), abdominal obesity based on WHR was 37.8% (95%CI; 33.7–42.1), and WC was 29.1% (95%CI; 25.2–33.1). More than half (54.3%) of the participants consumed an adequate dietary diversity (DDS ≥4). After adjustment for potential confounders, the prevalence of abdominal obesity by WHR decreased with higher DDS among male (APR = 0.42; 95% CI, 0.22–0.77) and female participants (APR = 0.63; 95% CI, 0.41–0.94). There were inconsistent positive associations between DDS and prevalence of overweight and general obesity among male and female. There was no association between DDS and abdominal obesity by WC. More than half of the pastoralists have consumed an adequate diversified diet. Given the inconsistent findings on associations between dietary diversity and obesity measures, this study suggests that targeting dietary diversity as an overweight/obesity prevention strategy requires careful consideration.