The objective of this study was to evaluate particle size distribution and ruminal in situ DM and starch disappearance of sorghum kernels cut in varied particle sizes. Unfermented kernels from 25 sorghum hybrids were harvested at various silage maturities and combined into 3 400g composites. Each composite was assigned to 1 of 3 treatments: whole kernel [1P], 2 [2P] pieces, or 4 [4P] pieces. Kernels were manually cut to achieve treatments using X-Acto knives. After cutting, kernels were dried in a forced air oven at 60°C for 48 h. Thereafter, geometric mean particle size (GMPS), surface area, and particle size distribution were determined using a Ro-Tap Shaker with 9 sieves with nominal apertures of 6.70, 4.75, 3.35, 2.36, 1.70, 1.48, 0.59 0.30 mm and pan. Subsequently, a ruminal in situ disappearance trial was performed to determine ruminal DM and starch disappearance with 3 lactating Holstein cows. Incubation times were 0, 6, 12, 48, and 120 h and treatments were triplicated within each cow. Polyester bags containing 5.00 ± 0.02 g of DM, were utilized to measure fractions A, B, and C, and to estimate the fractional disappearance rate (K_d) of fraction B and the effective ruminal disappearance (ERD). Data were analyzed using PROC MIXED of SAS with the fixed effect of treatment and the random effect of cow. Measurements of GMPS were 2152.0, 1695.5, and 1277.5 µm for 1P, 2P, and 4P, respectively. Fractions A (P < 0.01), B (P < 0.01), and K_d (P < 0.01) of DM increased with a reduction in particle size, whereas fraction C (P < 0.01) decreased. Likewise, greater fraction A (P < 0.02), B (P < 0.01), and K_d (P < 0.02) of starch were observed with a reduction in particle size. Moreover, reductions in particle size enhanced ERD of DM (P < 0.01; 3.12, 17.8, and 23.9% DM for 1P, 2P, 4P, respectively) and starch (P < 0.01; 15.2, 22.6, 39.7% of starch). These results underscored that more extensive processing of sorghum kernels improves ruminal DM and starch disappearance through increased surface area for microbial attachment and fermentation.