Heat treatment of wood is a promising alternative in improving its dimensional stability. The action of heat ensures the good quality of the treated wood product, with better performance in environments with high humidity. To prove the positive effect of this treatment, a test in which the specimens are weathered for a certain period of time termed as natural aging was performed. The aim of this study was to evaluate the effect of aging on heat-treated medium-density fiberboard (MDF) panels. Commercial MDF panels produced with pinewood adhesive and urea-formaldehyde were used. The experiment included seven test treatments [at 200, 225, and 250°C heat temperatures for 5 and 10 min] and a control treatment (without heat treatment). The products subjected to these treatments were weathered for 40 days, and climatological data were monitored daily. The results suggested that: 1) There is a decreasing trend in density with increasing time and temperature; 2) the treatment time and temperature had no effect on the ownership of the static bending for modulus of elasticity (MOE); 3) the time period is correlated with the treatment temperature for modulus of rupture (MOR) property; and 4) the thermal treatment of MDF panels did not allow the maintenance of the properties of MOR and MOE static bending strength after natural aging.