A steam explosion degumming method coupled with the 16 (44) orthogonal array design was used to investigate the efficient retting of fibers. Four parameters were examined to determine the residual gum and lignin content of retted fibers, and the optimum extraction conditions were determined to be the following: banana fiber moisture content of 10%, 1.2% NaOH, steam pressure of 1.75 MPa, and residence time of 90 s. Under optimized conditions, the experimental yield of residual gum (5.47 ± 0.22%) and lignin (3.78 ± 0.12%) agreed closely with the predicted yield. The chemical composition of the fibers was analyzed, and the retted fibers exhibited an increase in the cellulose content and a decrease in the lignin and hemicellulose contents. This result was further confirmed by XRD and Fourier transform infrared spectroscopy. The scanning electron microscopy analysis of the treated fibers showed a change in their surface morphology compared with that of the raw fibers. Their thermal characterization showed an enhanced thermal stability of the retted fibers compared to the raw fibers. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40598.