This study presents a combined experimental and numerical investigation of fused filament fabrication (FFF)-printed polyether ether ketone (PEEK) plates subjected to quasi-static and high-velocity impact loadings. Izod impact, quasi-static punch-shear (QS–PS), and high-velocity projectile impact tests were conducted on specimens with different infill patterns, namely line, grid, cubic, and hexagonal configurations. High-velocity impact experiments were performed using a two-stage gas gun at an impact velocity of 100 m/s. Infill architecture influences quasi-static and low-rate impact performance. The hexagonal pattern exhibited the highest Izod impact strength (ca. 24 kJ/m²) and punch-shear strength (ca. 12 MPa), demonstrating improved load distribution and energy absorption capability. Under high-velocity impact, infill geometry becomes less influential, indicating comparable ballistic responses. This reduced sensitivity to infill pattern is attributed to rapid stress-wave propagation and extremely short interaction times, which limit progressive deformation within the internal structure. Finite element simulations using a solid PEEK model further support these findings, showing similar stress distributions and penetration behavior across all configurations. The results demonstrate that while infill geometry plays a critical role under quasi-static loading, its effect diminishes under high-velocity impact, where the response is predominantly governed by the intrinsic material behavior of PEEK.