The grey fantail (Rhipidura albiscapa) is a common Australian flycatcher, yet no detailed reports have been made of its breeding ecology. A population of grey fantails was studied over four seasons in the Australian Capital Territory. Males had large testes and pronounced cloacal protuberances, morphology suggestive of sperm competition. Although two polyandrous trios were observed, most individuals bred as part of a season-long monogamous pair, suggesting that extra-pair copulation may be the principal cause of sperm competition. Indeed, behavioural observations revealed that males regularly intruded other territories, targeting those with building, rather than incubating, females. Intruding males were observed harassing, attempting to copulate and successfully copulating with resident females. Males did not mate guard, but regularly attacked their mates during each building attempt. Despite the probability that extra-pair paternity is common in this species, grey fantails were monomorphic and monochromatic, with a high level of paternal care. Nest depredation was common, with 83% of all clutches depredated before fledging. High levels of male care in care in this species may be better explained by an increase in fledging success associated with high male contribution to offspring care than confidence of paternity.