In this study, the effect of various micro and nano-sized particles on the mechanical and adhesion prop-erties of a commercial non-pigmented polyester-TGIC powder coating was studied. Different coatingformulations containing various wt.% of aluminum hydroxide (alumina) particles, TiO2and two differenttypes of fumed silica nanoparticles were prepared via a two-stage process. Tensile strength measure-ments, DMTA analyses and vertical pull off adhesion test were conducted to evaluate mechanical andadhesion properties of the powder coating samples. The results revealed that the mechanical properties of the powder coating samples were improvedwith respect to the particles loading up to 2 wt.%. The extent of this effect depends on the weight fractionand size of the particles. The fumed silica nanoparticles with dimethyl dichlorosilane treatment revealedto be more effective to enhanced mechanical and adhesion properties due to relatively better dispersionand plausible chemical interactions between silane treatment on the nanoparticles surface and polymericmatrix. The fluctuation in the mechanical properties was also observed as the particles content furtherincreased up to 3 wt.% due to an undesirable dispersion of the particles and in turn to the presence ofaggregates, air pockets as well as discontinuity in the film.Eventually, the results revealed that pre-dispersion of nanoparticles in an appropriate solvent such asethanol with the aid of ultrasonic irradiation, is a useful and applicable method before addition to a pow-der coating formulation. In fact, applying ultrasonic irradiation facilitates breaking down of nanoparticlesaggregations to possible primary particles.