The Discrete Element Method (DEM) is widely used to simulate biomass material handling, but accurate simulation requires appropriate parameter calibration. This study calibrated DEM parameters for fibrous and irregular biomass materials, including sawdust (SD), tree leaves (TL), and a 70:30 SD:TL mixture, which exhibit more complex flow behavior than conventional granular materials. A fixed funnel method was employed to measure the static AoR of sawdust (SD), tree leaves (TL), and their mixture. For TL, three material samples (T1-T3) were tested with six repetitions, giving 18 AoR measurements. For SD and the mixture, two samples each (S1-S2 and M1-M2) were tested with six repetitions per sample, yielding 12 measurements per material. The AoR results are reported as mean ± standard deviation were 39.28° ± 0.88° (SD), 41.72° ± 1.70° (TL), and 40.08° ± 1.03° (mixture). DEM simulations (Hertz–Mindlin with JKR cohesion) were tuned by comparing simulated and experimental AoR. Initial parameter sets were defined through literature review and tested in DEM, with the best-fitting parameters identified by comparing simulated AoR with experimental results. The best-fit parameters were as follows (values reported in the order of sawdust, tree leaves, and mixture, respectively): Poisson’s ratio (0.300, 0.300, 0.260), shear modulus in MPa (6.000, 10.000, 7.684), restitution coefficient (0.020, 0.002, 0.067), static friction (0.760, 0.600, 0.660), rolling friction (0.120, 0.070, 0.080), and JKR surface energy in J/m2 (0.120, 0.100, 0.098). The relative error between the simulated and experimental AoR was 0.63% for sawdust, 0.15% for tree leaves, and 1.29% for their mixture. These results provide valuable insights for accurately simulating the behavior of biomass materials, such as sawdust and tree leaves, in DEM-based processing systems.