In this study cellulose acetate (CA) was modified with 4,4,-diphenylmethane diisocyanate (MDI, an N-halamine precursor) in solution to form chemical bonds between CA and MDI to avoid the potential release of biocides from CA. Nanofibers were obtained by electrospinning the CA-MDI solution. The obtained CA-MDI nanofibers were characterized by FT-IR, SEM, TGA and DSC. TGA and DSC data indicated that the CA-MDI nanofibers before and after chlorination had good thermal stability compared with CA nanofibers. 58% of active chlorine was lost after 2 h of UVA irradiation, and most of the active chlorine was lost after 4 h of UVA irradiation. However, about 85% of the chlorine could be regenerated by rechlorination after 24 h of UVA irradiation. The active chlorine of the chlorinated nanofibers released slowly in water. The chlorinated CA-MDI nanofibers showed excellent antimicrobial properties against Escherichia colt O157:H7 and Staphylococcus aureus within brief contact times. Also, the chlorinated CA-MDI nanofibers showed good biocompatibility. (C) 2015 The Korean Society of Industrial and Engineering Chemistry. Published by Elsevier B.V. All rights reserved.