The objective of this study was to evaluate how canopy heights (1.00, 1.40, 1.80, 2.20 and 2.60 m) affect fiber digestibility of elephantgrass (Pennisetum purpureum cv. Cameroon). The experiment was conducted in 25 plots with 6 rows each in Lavras, MG, Brazil. Harvests were performed from Oct/2014 to Oct/2016. The experimental period was divided in 4 periods, 2 rainy seasons (RS) and 2 dry seasons (DS). The plants used for the evaluations were harvested at soil level. Forages were analyzed for aNDF with the Ankom procedure with NDF solution containing amylase and sulfite. Fiber digestibility was measured by the total-tract NDF digestibility (TTNDFD) in vitro method. Indigestible NDF (iNDF) of the samples was obtained via 240 h in situ incubation in 2 cannulated dairy cows. A randomized complete block design with 5 replications was used. Data were analyzed with PROC MIXED in SAS, and canopy height (CH), season and its interaction were considered fixed effects. There were differences between all variables (P < 0.01) between RS and DS. No differences in any of the measured variables were seen between the 2 RSs or between the DSs. Regressions to determine linear relationships were performed using PROC REG of SAS. For the RSs, there was a linear increase on aNDF (R² = 0.82; P < 0.001) and iNDF (R² = 0.84; P < 0.001) content with the increase of the CH. A linear (R² = 0.74; P < 0.001) reduction in TTNDFD values occurred with the increase of the CH, with the same reduction observed for the digestion rate k_d (R² = 0.77; P < 0.001). During the DS, the NDF and iNDF values were greater (P < 0.0001) than during the wet seasons for all treatments. NDF and iNDF also increased linearly (R² = 0.79; P < 0.001 and R² = 0.81; P < 0.001 respectively) as the CH increased during the DS. The TTNDFD of plants harvested during the DSs were lower (P = 0.0065) than in plants harvested during the RS, and the TTNDFD values decreased linearly (R² = 0.72; P = 0.0423) with the increase of the CH. The digestion rate also decreased linearly (R² = 0.724; P = 0.0223) with the increase in CH. As CH increased, the fiber digestibility of elephantgrass decreased.