Following dispersal from 1 group, individuals may join other established social groups. Such intergroup transfer may increase access to potential mates and decrease mate competition. We used data from 402 individuals to examine patterns of intergroup transfer in prairie voles (Microtus ochrogaster). Nearly 32% of established social groups (single female units, male–female pairs, or communal groups of at least 2 adults of the same sex) were joined by 1 or more individuals. Most individuals (76%) that joined social groups were wanderers that were either unmarked, recently marked during grid trapping, or marked transients; 70% were males. Joining a group was not contingent upon recent disappearance of residents. Total number of residents positively affected the probability of a female joining a social group, whereas number of adult female residents and population density negatively affected it. Some individuals (24%) moved directly from one group to another without an intervening wandering stage; we refer to these instances of intergroup transfer as direct transfers. Most direct transferers moved into nearby groups, but not the closest group. Males were more likely than females to directly transfer into groups with potential mates and without potential competitors. Thus, males directly transferred in a manner consistent with maximizing reproductive opportunities. In contrast, 25% of females directly transferred into groups without potential mates and 96% into groups with at least 1 adult female. Females may be less constrained by group composition with respect to potential mates because wandering males, with which females can mate, are prevalent. All-male groups almost never occur in our population, so females probably cannot avoid joining groups with competitors.