In this work, we evaluate the effect of spherical silica nanoparticles on the thermal transitions and structure of poly(4-benzoic acid-co-ethylene teraphthalate) (PHBA-PET) films. Composite films were produced by direct melt-blending of the polymer with up to 1.5 vol% loadings in a Thermo-Haake MiniLab2 twin-screw extruder. Thermal transitions were determined by differential scanning calorimetry and thermogravimetric analysis. Structure and morphology were analyzed by a combination of polarized optical microscopy, small-angle x-ray scattering (SAXS), and scanning electron microscopy. No significant changes were observed on the glass transition temperature, nevertheless the melting point showed a small tendency toward higher values at higher loadings. The nematic range decreased upon addition of particles, but was mostly unaffected by concentration. The maximum rate of degradation was displaced up to 30 ºC. A detrimental effect on the internal ordering of the polymer was also observed, as suggested by the reduction of the characteristic SAXS peak. Micrographs show a smooth film surface and straight fracture planes (i.e. no fibrils). Silica particles improved the thermal properties of the polymer, yet as the loading increase results suggest a reduction of the nematic range and order.