The target of the presented study is to investigate the permeability of polypropylene-fiber-reinforced concretes, with and without silica fume (SF), using various mix proportions. This effort was made to clarify the contradicting published literature data. The considered fiber volume fractions were 0.1 %, and 0.5%. Silica fume was used as 10% replacement of cement weight. Different water and air curing condition were carried out to study their effect on the permeability of concrete. Cement contents of 350 kg/m3 or 450 kg/m3 were utilized. Water/cement ratios of 0.30, 0.40, and 0.50 were considered in the program. Results showed that the incorporation of polypropylene fibers had varying effects on the permeability of concrete depending on cementitious material content, w/c ratio and curing regime. Silica Fume, as generally recognized, improved both concrete strength and impermeability. Polypropylene fiber (PPF) did not, unconditionally, improve concrete resistance to flow. When cementitious material content was increased and w/c ratio was lowered PPF enhanced concrete impermeability. Otherwise, PPF did not improve concrete impermeability. It is also noticed that polypropylene fibers improved the performance of concretes subjected to insufficient curing periods, compared to similar mixes without fibers.