The goal of this study was to investigate the use of old newsprint (ONP) fiber as raw material for laboratory made medium density fiberboard (MDF). Effect of ONP fiber mixed with virgin aspen (Populus deltoides) fiber and the press time (3, 4, and 5 min) on the properties of MDF panels were determined. Panels were produced using aspen fibers in surface layer and combination of aspen fibers and ONP fibers in core layer. Physical (thickness swelling) and mechanical properties of the panels were determined according to the procedure of EN standards. This study showed reduction in bending strength and internal bond strength of the panels as ONP fiber was loaded from 35 to 70% in core layer. Thickness swelling of MDF panels was drastically increased with addition of ONP fiber to the panels’ furnishes. Based on the findings of this study, it appears that ONP can be considered as a potentially suitable raw material for manufacturing MDF products without having any significant adverse influence on the panel properties.