Background Foster families may represent an alternative model for dependent older adults in many countries where nursing homes are insufficiently developed. This study aimed to assess the prevalence of malnutrition and its determinants in older adults living in foster families in Guadeloupe (French West Indies). Methods This cross-sectional study was gathered from the KASAF (Karukera Study of Ageing in Foster families) study (n = 107, 41M/66F, Mdn 81.8 years). Nutritional status was assessed with the Mini Nutritional Assessment Short‐Form (MNA‐SF). Clinical characteristics and scores on geriatric scales (Mini-Mental State Examination (MMSE), Activities of Daily Living (ADL), Short Physical Performance Battery (SPPB), Center for Epidemiologic Studies- Depression (CESD) and Questionnaire Quality of Life Alzheimer’s Disease (QoL-AD)) were extracted. Bivariate analysis and logistic models adjusted for age and gender were performed to test the association of nutritional status with socio-demographic variables and geriatric scales. Results Thirty (28.0%) older adults were malnourished (MNA-SF score ≤7). In bivariate analysis, malnutrition was associated with an increased prevalence of cardiovascular diseases (46.7% versus 19.5%, p = 0.004), the presence of hemiplegia (30.0% versus 6.5%, p = 0.003), a poorer cognitive status (MMSE score 4.7 ± 7.1versus 9.7 ± 10.7; p = 0.031), higher risk of depression (CESD score 27.3 ± 23.0 versus 13.5 ± 14.4; p = 0.035) and dependency (ADL score 1.9 ± 1.9 versus 2.3 ± 2.1; p<0.001). Malnutrition was also associated with lower caregivers’rating of QoL (QoL-AD score 21.8 ± 6.4 versus 26.0 ± 5.7; p = 0.001) but not by older adult’s rating (24.1 ± 11.2 versus 28.3 ± 7.7; p = 0.156). Similar associations were observed in logistic models adjusted for age and gender. Conclusion Malnutrition was common among foster families for older adults. Special attention towards the prevention and treatment of malnutrition in older adults from cardiovascular diseases, cognitive impairment, dependency and depression is necessary in this model of dependency support.