Conventional static tests are often insensitive to the dynamic behavior of pharmaceutical powders during manufacturing. This study developed and optimized a particle image velocimetry (PIV) method using high–power light–emitting diodes (LEDs) to evaluate powder flowability during blending. Illumination intensity, contrast–limited adaptive histogram equalization (CLAHE) window size, and interrogation window size were systematically optimized using spherical beads with uniform optical properties to ensure stable image quality and reliable vector analysis. The optimal conditions were 65,125 lx at 0.35 m, 16 px CLAHE, and 32 px interrogation, which produced sharp particle boundaries, high correlation quality, and reproducible vector fields. The optimized LED–based PIV system was then applied to three grades of microcrystalline cellulose. PROSOLV^® SMCC 50, rated poor by static indices, showed the highest velocity magnitude (1.10 px/frame) with coherent convective flow. Although static tests classified Avicel^® PH–102 and PH–112 as very poor, with Carr’s indices of 39.22% and 42.59%, dynamic analysis showed different behavior: PH–112 had a higher velocity magnitude (0.52 px/frame), while PH–102 had the lowest (0.32 px/frame), with irregular motion and localized stagnation. These findings show that the optimized LED–based PIV system enables real–time, spatially resolved, and non-invasive assessment of dynamic powder flowability in pharmaceutical manufacturing.