From 2013 to 2023, over 90% of the population in Tanzania fell below the WHO-recommended fruit and vegetable (FAV) intake of >5 servings/day. Variation between wet and dry seasons further influences dietary intake and stability, which has implications for nutritional adequacy and non-communicable disease (NCD) risk, especially in rural areas. However, evidence on seasonal FAV intake and its determinants in Northwestern Tanzania is limited. This study aimed to describe the adequacy and seasonality of FAV intake and examine associations with socio-demographic and health factors in Northwestern Tanzania. Data were collected from 2012-2013 as part of regular serological surveys in the Magu Health and Demographic Surveillance System (HDSS), including 7,620 participants. Three multinomial logistic regression models were used to assess associations between seasonal FAV intake and socio-demographic and health characteristics. Most participants (96.1%) reported inadequate intake in both seasons. FAV adequacy and intake measures were significantly higher in the wet season compared to the dry season. In adjusted analysis, females and overweight/obese individuals had a lower relative risk of inadequate intake, whereas rural residents and adults aged 50 years or older had a higher risk. These findings emphasize a need for further research and interventions incorporating seasonal variation on FAV intake, with a focus on vulnerable groups and improving year-round accessibility of culturally relevant, affordable FAV within local environmental contexts.