The effect of molasses fortifying concentrate with rumensin (MFC+R) supplementation on the average daily gain (ADG) and cost effectiveness of Brahman in feedlot was evaluated at South Davao Development Project (SODACO), Davao City for 6 months. Thirty-eight (38) Brahman feeder stocks were randomly assigned to the Treatment and Control groups using a Randomized Complete Block Design (RCBD). The animals in the Treatment group were supplemented with molasses mixed with MFC+R at a ratio of 1 kg MFC+R to 15 kg molasses. Animals in the Control group were provided with the same amount of molasses but without MFC+R. The result showed that MFC+R supplementation had a positive effect on the average daily gain (ADG) of the animals. The ADG of the Treatment group was significantly higher (P<0.05) compared with the Control (0.73 kg/day vs 0.40 kg/day). Furthermore, the Control group consumed 25% more roughage compared to the Treatment group. The partial cost and return analysis revealed that the Treatment group earned more per animal compared with the Control group during the 124-day fattening period.