<p> This study examines the influence of yarn breakage, specifically the number of layers and their location, on the low-velocity impact response and post-impact compression performance of 3D woven composites. Specimens with yarn breakage on either the upper or lower surface were impacted at two different energy levels. Damage evaluation was conducted using C-scan, μ-CT, and DIC methods. The results indicate that yarn breakage on the lower surface (tension zone) leads to notable reductions in initial stiffness (up to 40.2%) and peak load (up to 33.4%), with a clear threshold effect when two or more layers are broken. This condition also resulted in significantly expanded damage area (up to 94.3% increase). In contrast, breakage on the upper surface (compression zone) mainly increased energy absorption (up to 84.4%) and permanent displacement (up to 65%) under high-energy impact. Additionally, compression-after-impact strength was approximately 11% lower for specimens with yarn breakage on the lower surface, where failure was governed by a damage network initiated by the yarn breakage. These findings provide concrete design guidelines for avoiding critical strength reduction and optimizing damage tolerance in composite structures containing yarn breakage defects, particularly for aerospace applications where impact resistance is crucial.</p>