Basalt fiber was first treated in a mixture of formic acid (FA) and dichloromethane (DCM) to reduce its diameter down to one micrometer. Electrospinning process was utilized to produce treated basalt fiber (TBF)-reinforced nylon 6,6/epoxy (NY/EP) hybrid nanofibril composites. NY/EP polymers have been dissolved in 80:20 mixture of FA/DCM solvent to form a homogenous solution. TBFs with different weight ratios of 5, 10, 15, 20, and 25 wt% were added to NY/EP (ratio of 5:1). The morphology of the hybrid nanocomposites was investigated by scanning electron microscopy and their compositions were analyzed using energy-dispersive X-ray spectroscopy. The thermal properties were studied by differential scanning calorimetry and thermogravimetric analysis. The mechanical properties of the hybrid nanocomposites, including tensile strength and modulus, are improved with respect to NY/EP hybrid nanofibers. An increase of 76% and 87% in tensile strength and Young’s modulus was acquired, respectively, at 15 wt% of TBF. Also, the addition of TBF increased the thermal stability of nanofibril composites.