This study aimed to determine the effectiveness of penoxulam herbicide in controlling weed and its effect on yield of rice (Oryza sativa L.) under direct seeding system. This study used a Randomized Block design with six treatments and carried out from Agusts - November 2014 in Tolai village, Torue Sub District, Moutong Parigi District. The treatments tested were the rates of active ingredient of penoksulam at 1.2 ml plot-1, 1.8 ml plot-1, 2.4 ml plot-1, 5.0 ml plot-1, 12.0 ml plot-1, and with no herbicide added (control). The experimental plots had a dimension of 4 m x 5 m each. The herbicide at the rates up to 12.0 ml plot-1 added at 3, 7 and 14 days after application only caused mild symptoms on the rice plants. The dominant weeds controlled by the herbicide included Fimbristylis miliacea, Echinochloa crusgalli, Ludwigia octovalvis, Monochoria vaginalis, Cyperus iria, Cyperus difformis, Leptochloa chinensis and Limnoharis. The effective rates of the herbicide that can increase the production was ranged from 1.2 ml plot-1 to 2.4 ml plot-1.