Abstract Objective It is generally thought that causes of undernutrition are multifactorial, but there are limited quantitative studies performed. We therefore examined a wide range of potential factors associated with undernutrition in community-dwelling older adults. Design Cross-sectional study. Setting Community-dwelling older adults (≥65 years) receiving home care in the Netherlands. Subjects Data on potential factors associated with (risk of) undernutrition were collected among 300 older adults. Nutritional status was assessed by the SNAQ 65+ instrument. Undernutrition was defined as mid-upper arm circumference <25 cm or unintentional weight loss of ≥4 kg in 6 months. Being at risk of undernutrition was defined as having poor appetite and inability to walk up and down stairs of fifteen steps, without resting. Results Of all participants, ninety-two (31·7 %) were undernourished and twenty-four (8·0 %) were at risk of undernutrition. Based on multivariate logistic regression analyses, the statistically significant factors associated with (risk of) undernutrition ( P <0·05) were: unable to go outside (OR=5·39), intestinal problems (OR=2·88), smoking (OR=2·56), osteoporosis (OR=2·46), eating fewer than three snacks daily (OR=2·61), dependency in activities of daily living (OR=1·21), physical inactivity (OR=2·01), nausea (OR=2·50) and cancer (OR=2·84); a borderline significant factor was depression symptoms (OR=1·83, P =0·053). Conclusions The study suggests that (risk of) undernutrition is a multifactorial problem and that associated factors can be found in several domains. These findings may support the development of intervention trials for the prevention and treatment of undernutrition in community-dwelling older adults.