Studies show that morningness preference and subjective well-being are positively related. However, little is known about potential factors that may underpin this association. In the present study, we explored the mediational role of general social support and its facets (family, friends, and significant other) in the relationship between morningness-eveningness and subjective well-being. The present study was conducted with a sample of 1,067 adults (51% women), with a mean (SD, range) age of 36.41 (9.95, 18-55) years. Our results corroborated earlier findings that morningness was positively associated with both subjective well-being and social support.Controlling for age and gender, we obtained significant mediation effects, showing that the association between morningness-eveningness and subjective wellbeing might stem, at least in part, from the higher levels of social support received by morning-oriented individuals. This may lead to the conclusion that social support is an important antecedent of the greater well-being reported by morning-oriented individuals.