The objective of this work was to evaluate the effects of soluble carbohydrate and protein supplementation on feed digestibility and rumen characteristics of swamp buffaloes fed total mixed fiber (TMF) silage by using an in vitro technique. A completely randomized design with 3 treatments (soluble carbohydrate (SCH) and protein ratio) and 6 replicates was used. Treatments consisted of total mixed fiber silage rations with SCH: protein ratio of 300 g : 300 g (1 : 1) (A1), SCH : protein ratio of 600 g : 300 g (2 : 1) (A2), and SCH : protein ratio of 900 g : 300 g (3 : 1) (A3). Measurements were taken on nutrient digestibility rates (dry matter, organic matter, crude protein, and crude fiber), fiber digestibility rates (NDF, ADF, cellulose, and hemicellulose), and rumen fermentation condition (concentrations of RAN, total VFA, acetate, propionate, butyrate, and methane and pH). Results showed that significant effects (P LT 0.05) of treatments were found on nutrient digestibility rates (dry matter, organic matter, crude protein, crude fiber, ADF, cellulose, and hemicellulose), rumen fermentation conditions (concentrations of RAN, total VFA, acetate, propionate, butyrate, and CH4). Meanwhile, no effects (P GT 0.05) of treatments were found on NDF digestibility and pH levels. It was concluded that TMF silage ration supplemented with SCH and protein ratio of 3 : 1 (900 g : 300 g) gave the best results in terms of nutrient digestibility rates and rumen fermentation condition of swamp buffaloes.