Harris's Hawks (Parabuteo unicinctus) are cooperative breeders, and groups of more than a pair have been reported from Arizona (49% to 83%) and New Mexico (51%). However, two studies (Griffin 1976, Brannon 1980) suggested that they breed in groups infrequently in Texas (5% and 13%). During a banding study from 2004–2014, I occasionally captured three or more adults at the same time and place, and I regularly observed groups of three or more adults. I undertook a study to determine sizes of breeding groups in south Texas in 2014 and 2015 in a mix of breeding habitats, primarily thorn scrub forest, but also parks, agriculture with forest and grassy plots, industrial areas, and urban areas. I determined that more than half (56%) of the 73 breeding groups I observed in south Texas were composed of three or more individuals, contrary to the results of the two earlier Texas studies, which may have underestimated group size because of fewer short visits compared to longer visits spent determining group size in this study.