Direct observations of small foxes are rare because of their secretive nature and nocturnal activity patterns. We observed 10 adult (≥1-year-old) San Joaquin kit foxes (Vulpes macrotis mutica) at night over a 7-month period that included the mating season to quantify the types, rates, and durations of social interactions. Of 191 interactions between members of this seasonally breeding, socially monogamous species, 52 were with adult foxes in the same social group, 43 with adult foxes from other known social groups, 48 with juveniles (<1 year old), and 48 with unknown foxes. Most interactions (n = 173), especially those between pair-mates, between females, and with juveniles, were affiliative. Agonistic encounters were rare (n = 18) and occurred mostly between males of different social groups and with unknown foxes. Interaction rates with social group members, most of which were pair-mates (88%), peaked in the months before the annual mating season, whereas those with non–social group foxes, most of which represented potential extrapair copulation partners (79%), peaked later and more sharply. The duration of interactions with adult social and non–social group foxes was highest during the mating season. Increased social interactions at this time may help foxes strengthen bonds with pair-mates and become familiar with potential extrapair partners.