Effects of alkali treatment and ammonium bicarbonate were studied relative to selected properties of medium-density fiberboard (MDF) panels. Wood fibers were subjected to alkali treatment with sodium hydroxide or sodium perborate monohydrate (SPM). The MDF panels were produced from untreated and alkali treated fibers with or without ammonium bicarbonate (ABC). The modulus of rupture (MOR), modulus of elasticity (MOE), internal bonding (IB), thickness swelling (TS), water absorption (WA), and limiting oxygen index (LOI) of the MDF were analyzed. The mechanical, physical, and fire resistance properties of MDF samples showed differences depending on the experimental parameters used. The lowest TS and WA values were found in the untreated-control group. The highest value for MOR and MOE was found for the group with the addition of 8% ABC. The IB values generally were higher than the untreated-control value. The highest value was determined in the group ABC8. Remarkably higher LOI values were achieved in the LOI test, especially for the groups with the application of both alkali treatment and ammonium bicarbonate.