Affiliation/agonism and social dominance are central factors determining social organization in primates. The aim of our study is to investigate and describe, for the first time, the intersexual relations in a nocturnal and cohesive pair-living prosimian primate, the western woolly lemur (Avahi occidentalis), and to determine to what extent phylogeny, activity mode, or the cohesiveness of pair partners shape the quality of social interactions. Six pairs of western woolly lemurs were radio-collared in the dry deciduous forest of northwestern Madagascar. More than 874 hr of focal animal sampling were conducted. All occurrences of social interactions involving a focal animal were recorded. The rate of affiliation between pair partners was significantly higher than the rate of agonism. Western woolly lemur pairs' interactions were extremely peaceful. All decided agonistic conflicts (N = 15) were exclusively initiated and won by the female. No female showed spontaneous submission toward her male partner. These results are in line with those of diurnal cohesive pair-living anthropoid primates. Findings support the hypothesis that social relations in pair-living primates are linked to the cohesiveness of pair partners in time and space irrespective of phylogeny and activity mode. Am. J. Primatol. 73:1261–1268, 2011. © 2011 Wiley Periodicals, Inc.