Abstract An experimental investigation is reported on the effect of fiber length distribution on gas holdup in a cocurrent air–water–fiber bubble column. Different combinations of 1 and 3 mm Rayon fibers are used to simulate different fiber length distributions. At a constant total fiber mass fraction, gas holdup generally decreases with increasing mass fraction of the 3 mm Rayon fiber while other conditions remain constant. Crowding factors estimated using four different methods ( N c = N c , A , N c * , N c , L , and N c , M ) and the parameters N c , L N f 0.2 0.8 and N c , M N f 0.2 0.8 are tested on their performance to quantify the overall effects of fiber mass fraction and fiber length and its distribution on gas holdup. N c , L N f 0.2 0.8 and N c , M N f 0.2 0.8 provide the best characterization of the fiber effects on gas holdup in the cocurrent air–water–fiber bubble column. The crowding factor estimated using the model-based average fiber length ( N c , M ) also provides a good characterization and is better than the other crowding factor definitions.