Recent studies suggest that differential human male investment in mating (male‐male competition and mate‐seeking behavior) and parenting effort may be associated with variation in testosterone levels. The Ariaal present an interesting test case because marital relations tend to be aloof and direct paternal care minimal by cross‐cultural standards. Polygyny is prevalent and increases with age, and the age‐set system highly structures the transition to marriage. A test of the effect of marital status on testosterone levels among the Ariaal involved 205 men aged 20 and older from a settled agropastoral community and nomadic populations. Each participant provided morning and afternoon saliva samples in which testosterone levels were measured, provided demographic background during interviews, and had anthropometrics taken. As predicted, during the dynamic ages (20–39) of transition from life as a bachelor and warrior to monogamous marriage, men with one wife had significantly lower testosterone levels than unmarried men. Contrary to prediction, however, polygynously married men did not have higher testosterone levels than their monogamously married counterparts. While variation in testosterone may be associated with mating effort in young Ariaal men, political networks and wealth may be better predictors of marital status in older men.