An adult male of the tick Amblyomma rotundatum Koch was collected on a naturally infested lizard, Tropidurus sp. (Squamata: Tropiduridae), at Monte Negro, State of Rondônia, Brazil. The tick’s identity was confirmed morphologically and by analysis of the second internal transcribed spacer of the ribosomal DNA. This is the third known male specimen of A. rotundatum, a species that has been shown to reproduce exclusively by parthenogenesis. The two previously reported male specimens seemed to be partially teratological or gynandromorphic, whereas the present specimen shows no visible genetic or developmental anomaly.