Carbon fibre-reinforced polyamide 6 (PA6) composites exhibit exceptional mechanical properties, making them a highly attractive material option for various industries. Their ability to combine the advantages of carbon fibres with the versatility of PA6 provides opportunities for lightweight, high-performance applications. This work presented the fabrication of a PA6/carbon fibre composition with carbon fibre was modified by two different chemicals: nitric acid and diglycidil ether bisphenol A (DGEBA). The tensile strength at break, flexural strength, Rockwell hardness and Izod impact were measured to compare the mechanical properties of composites based on the PA6 matrix with two different modified carbon fibres. The morphology of PA6-based composite with different modified carbon fibres was observed by scanning electron microscopy. The results showed that PA6 is more compatible with acid-modified carbon fibre than DGEBA-modified carbon fibre and unmodified carbon fibre. In comparison to composite materials containing unmodified carbon fibre and DGEBA-modified carbon fibre, composite containing acid-modified carbon fibre increase tensile strength (16–38% and 7–15%, respectively), flexural strength (18–66% and 51–70%, respectively), Izod impact (23–65% and 32–78%, respectively) and Rockwell hardness (50–400% and equivalence, respectively).