Creating polymeric materials that are both structurally customizable and flame-resistant while also possessing superior mechanical and thermal characteristics has long posed a challenge for manufacturers across industries. In this study, we successfully synthesized titanium carbide (Ti3C2) MXene on the surface of a metal–organic framework (HKUST-1) to create a polyamide 12 (PA12) composite. This composite demonstrated improved mechanical strength and fire safety properties. Our thorough evaluation of the PA12/MXene-on-HKUST-1 composite revealed significant reductions in the total heat release (by 18.5%), peak heat release (by 26.1%), and total smoke emission (by 28.1%). Furthermore, the incorporation of MXene-on-HKUST-1 resulted in improved tensile and dynamic mechanical characteristics. These findings shed light on the underlying mechanism behind MXene-on-HKUST-1′s enhancement of the mechanical and flame-retardant properties. With the use of selective laser sintering, this work presents a promising technology for the development of high-performance MXene-reinforced PA12-based flame-retardant composites.