Ruminants produce methane gas which is an energy loss to them, and also one of the greenhouse gases which cause global warming. This study assessed the effect of varying levels of Morinda lucida Benth leaf powder (MLLP) on methane production and rumen fermentation parameters using in vitro technique. Six concentrate diets were formulated to contain MLLP as an additive at levels 0, 2, 4, 6, 8 and 10mg g-1 DM. Fresh Panicum maximum Jacq. Leaves were air dried to constant weight, milled and combined with each of the concentrate diet in the ratio 60 : 40 to serve as the substrate for the in vitro study. Incubation was carried out for 48 hours with 12 replicates per treatment in a completely randomized design. Dana obtained were subjected to one-way analysis of variance and significant means were separated using the Duncan multiple range test. Results obtained showed that MLLP contained saponin (8.62%), alkaloids (3.48%), tannin (511.4 mg 100 g-1), phenolic acids (328.15 mg 100 g-1), oxalate (110.58 mg 100 g-1), cyanogenic glycoside (4.34 mg 100 g-1), flavonoids (595.63 mg 100 g-1) and trypsin inhibitor (4.35 TIU g-1). Inclusion of MLLP up to 10 mg g-1 in the diet did not (P > 0.05) affect metabolizable energy, short chain fatty acids, total volatile fatty acids production and pH. However, net gas production, methane production, in vitro organic matter digestibility, in vitro dry matter digestibility and ammonia nitrogen concentration decreased (P < 0.05) at 8 and 10 mg g-1 DM. The study therefore concluded that MLLP could be used to manipulate rumen fermentation at 2 mg g-1 DM to depress methanogenesis without negative effect on dry matter digestibility and ammonia nitrogen concentration.