The objective of this study was to evaluate the effects of environment (i.e., growing conditions) and genotype on fiber digestibility of corn plant tissues. This study was performed on a 200-cow dairy farm located in Virginia. In 2 cornfields (i.e., blocks), one conventional (CONV) and one brown midrib (BMR) corn hybrid was planted in plots (4.5 m × 30 m). Two environments were targeted; a limiting environment (POOR) that consisted of planting 100,000 seeds/ha (i.e., high population) and fertilizing with 163 kg N/ha (i.e., low fertilization), and a non-limiting environment (GOOD) that consisted of planting 60,000 seeds/ha (i.e., low population) and fertilizing with 214 kg/ha (i.e., high fertilization). At tasseling (EARLY) and early-dent (LATE) stages of maturity, 5 plants from each plot were cut by hand, and stems, leaf-sheaths, and leaf-blades from phytomers 9 (LOWER) and 16 (UPPER) were dissected and frozen for analysis. Tissues were analyzed for in vitro apparent dry matter digestibility (IVDMD) and for in vitro neutral detergent fiber digestibility (IVNDFD). All variables were analyzed with Proc MIXED of SAS, and the statistical model included the fixed effects of environment, genotype, maturity, phytomer, and all their interactions and the random effects of field (i.e., block), and the interactions of field by environment by hybrid and field by environment by hybrid by maturity. IVDMD was greater for BMR than for CONV (75.7 vs. 61.8%; P < 0.01) and for EARLY than for LATE (77.7 vs. 59.8%, P < 0.01) but was not affected by environment (68.8%; P > 0.19). Within the plant, IVDMD was greater for UPPER than for LOWER phytomers (77.4 vs. 60.2%; P < 0.01). IVNDFD was greater for BMR than for CONV (68.1 vs. 54.0%, P < 0.01) and for EARLY than for LATE (72.3 vs. 49.8%; P < 0.01) but was not affected by environment (61.1%; P > 0.65). Within the plant, IVNDFD was greater in UPPER than for LOWER phytomers (70.2 vs. 51.9%; P < 0.01). In conclusion, while genotype, maturity, and tissue height within the plant had substantial effects on IVDMD and IVNDFD, environment had no effects on IVDMD and IVNDFD.