The present study explores whether different structural (presence of partner and children) and functional (amounts of instrumental and emotional support provided by partner and children) family characteristics buffer the influence of chronic diseases on physical functioning. Logistic regression analyses were performed in a population-based sample of 2830 community-dwelling elderly people with chronic diseases as independent variable, and mobility difficulties as dependent variable, for separate strata of family characteristics. The presence of buffer effects was ascertained by comparing the associations between disease variables and mobility difficulties across the strata of family characteristics, using the odds ratios and 95% confidence intervals. Living together with a partner appears to buffer the association between the presence of one chronic disease and mobility difficulties, but no such effect is present among subjects with more than one disease. Regarding specific chronic diseases, partner presence has a beneficial influence only on the association between stroke and mobility difficulties, regardless of whether the partner provides little or much support. For patients with chronic non-specific lung disease (asthma, chronic bronchitis or pulmonary emphysema), a small amount of instrumental support (help with daily chores in and around the house) received from the partner is associated with a higher risk for mobility difficulties, compared to patients who receive a large amount of instrumental support and to patients who are not living with a partner. Neither the presence of children, nor the amounts of support received from them, influences associations between specific chronic diseases and mobility difficulties. The present study provides limited evidence supporting a buffer effect of family characteristics on the association between chronic diseases and mobility. Only in elderly people with a relatively low burden of disease does family support mitigate the adverse effects of disease on physical functioning.