Polyethersulfone (PES) and polytetrafluoroethylene (PTFE) blend composites reinforced with sodiummontmorillonite (Na-MMT) nanoparticles were prepared by cold molding and vacuum sintering. The effects of the Na-MMT content on the thermal, nanomechanical, and tribological properties of the Na-MMT/PES/PTFE ternary composites were investigated in detail. The results indicate that at the optimal content, Na-MMT nanoparticles can be uniformly dispersed in the PES/PTFE binary blend composites and generate strong interfacial bonding with the polymeric matrix. Both the thermal stability and the nanomechanical properties of the PES/PTFE binary blend composites are clearly improved by the incorporation of Na-MMT nanoparticles. Among these PTFE-based composites, the Na-MMT/PES/PTFE ternary composite containing 10.0 wt% of Na-MMT nanoparticles exhibits the optimal friction and wear performance. Compared with those of the PES/PTFE blend composite, the friction coefficient (μ = 0.16) and wear rate (k = 2.63 × 10 −14 m 3 /(N•m)) of the 10.0 wt% Na-MMT/PES/PTFE ternary composite are 19.1% and 97.2% lower, respectively. The significant enhancement of the wear resistance of the Na-MMT/PES/PTFE ternary composite is attributable to the formation of PTFE self-lubricating transfer films. The transfer films generated on the worn surfaces of GCr15 steel balls can prevent direct contact between the PTFE composites and their metal counterparts, thereby protecting the polymer composites from damage.