OBJECTIVE: To evaluate the effects of neuropilin-1 (NRP-1) on bladder cancer progression. STUDY DESIGN: Four siRNA expression vectors were constructed to silence NRP-1 expression in bladder cancer cell lines in vitro. Meanwhile, the cell characteristic was also performed. Moreover, in vivo, we also explored NRP-1 roles in bladder tumor by tumorigenesis experiments in nude mice. RESULTS: In vitro, NRP-1 expression at mRNA and protein levels in the bladder cancer cell lines were both decreased after siRNA treatment. Meanwhile, the cell proliferation also decreased in the siRNA group as compared with the negative and blank groups. Meanwhile, in vivo of the nude mouse, siRNA treatment could suppress the gaining proportion of mouse body weight, tumor volume, and tumor weight. CONCLUSION: Targeting NRP-1 siRNA can effectively inhibit NRP-1 expression both at mRNA and protein levels in bladder cancer cell lines. Silencing NRP-1 could significantly inhibit bladder cancer cell line proliferation both in vitro and in vivo. © 2018 Science Printers and Publishers, Inc.