Common mistakes when unwrapping PBR 3D models include inefficient UV space use, overlapping UVs, poor seam placement, and misaligning with texture resolution needs.
Inefficient space wastes texture area (e.g., too much empty space), reducing detail. Overlapping UVs cause texture artifacts since multiple faces share the same pixels. Poor seams—like on visible or high-detail parts—make seams noticeable in renders. Misaligned resolution leads to blurry textures (UVs too small) or wasted memory (UVs too large).
For beginners, use software UV packing tools, practice with simple shapes, and check for overlaps in the UV editor—small steps fix most common issues.