The concept of structural toughening of composites by three-dimensional (3-D) fiber architecture is demonstrated. Polyetherketone (PEEK) matrix in filament form was commingled with carbon fiber before preform fabrication and composite consolidation to facilitate matrix introduction into the 3-D fiber network. The effect of matrix viscosity was found to be essential for effective fiber wetting in the 3-D fiber network. The tolerance of 3-D composites to damage induced by open holes and by impact was investigated under tensile and compressive loading. 3-D reinforced composites were found to have higher compression after impact strength and an order of magnitude lower damage area under 13 J/mm impact energy in comparison to laminated PEEK/carbon composites. This high level of damage tolerance is due to the lack of delamination inherent to 3-D reinforced composites.