Background and Objective: Though the exogenous fibrolytic enzyme, cellulase has been experimented with temperate feed stuffs, experiments on tropical wild grasses are very limited. Enzyme feed specificity is one of the crucial point that should be investigated deeply for the better utilization of enzymes in ruminant feeding. Hence, this study was carried out to investigate the effect of supplementation of cellulase enzyme on diet digestibility and growth performance of female goats (ewes) fed with wild guinea grass (Panicum maximum ecotype A). Methodology: Eight, 18 months old ewes (initial body weight = 19.40±3.03 kg) were used. The ewes were blocked into two groups based on body weight and randomized within the block for the treatment with Exogenous Fibrolytic Enzyme (EFE) and for the control. The whole experimental period was 180 days, consisted with two 90 days trial. In both trials, measurements of body weight were recorded in 2 week intervals and total feces and spot urine sampling were done for 7 days. All data were analyzed using IBM SPSS 20.0 Statistics software through one way analysis of variance (ANOVA) and all pairwise (Least significance difference (p<0.05)) comparisons. Results: Average Daily Gain (ADG) gram per day per animal in EFE group was significantly higher (p<0.05) than the control group where no difference was observed when ADG is expressed in terms of metabolic body weight. Intake (gram per day per animal) of Dry Matter (DM), Organic Matter (OM) and Neutral Detergent Fiber (NDF) (approximately by 8, 10 and 10%, respectively) were improved significantly (p<0.05) where no difference was observed in Crude Protein (CP) intake. Apparent DM and NDF digestibility enhanced (both by around 11%) significantly (p<0.05) while there was no difference observed in OM and CP digestibility. Both urinary creatinine and allantoin expressed either as mmol LG 1 or mg LG 1 significantly improved (p<0.05) with EFE supplementation. Conclusion: It is concluded that the supplementation with EFE for ewes is beneficial in means of ADG, intake and digestibility of DM and NDF and urinary allantoin production.