Reproductively mature male Dionda diaboli, the Devils River minnow, exhibited agonistic and courtship behavior in presence of conspecifics under laboratory conditions. Dionda diaboli spawned over small trays of gravel and did not use a cavity or a crevice. Devils River minnows were non-communal, territorial, broadcast spawners and agonistic behavior consisted of chases, parallel swims, lateral displays, circle swims, and head butts. Courtship behavior consisted of a male approaching a female and pushing her down toward the substrate (male-female approach) prior to spawning. Spawning did not occur until a male had established dominance in the hierarchy.