Using daily diary data from 28 later life couples where one spouse had diabetes and osteoarthritis, we examined crossover effects of target spouses' daily activity limitations and their partners' daily mood. On days when target spouses' daily activity limitations were higher than average, partners' positive mood decreased and negative mood increased; when target wives' limitations were higher than average, husbands' positive mood was higher. Marital happiness and frequency of telephone conversations of target spouses buffered some relations. Results advance our understanding of daily health processes within later life marriages by identifying crossover effects of activity limitations of an ill spouse with the mood of their partner and underscore the role of marital happiness and social contacts in buffering these associations.