Researchers have long debated the mechanisms underlying the learning of syntactic structure. Of significant interest has been the fact that passive constructions appear to be learned earlier in Sesotho than English. This paper provides a comprehensive, quantitative analysis of the passive input Sesotho-speaking children hear, how it differs from English input, and the implications for learning the passive. The findings indicate that the more frequent use of both the passive and the by-phrase in Sesotho child-directed speech, in conjunction with the non-ambiguous passive morpheme, may together facilitate earlier access to thematic roles (agent, patient), thereby promoting early implicit learning of the passive. The implications for the acquisition of syntactic structure more generally are discussed.