Accumulating evidence shows that circular RNAs (circRNAs) function as microRNA sponges that regulate gene expression in the progression of human cancers. However, the roles of circRNAs and functional miRNA sponges in bladder cancer (BC) remain largely unknown. In the present study, we applied bioinformatics methods and hypothesised that miR-146b may target the 3'-untranslated region (UTR) of CARMA3 mRNA and circINTS4 may serve as a sponge for miR-146b in BC tumorigenesis. Expression of circINTS4 was significantly increased in miR-146b-downregulated BC tissues and cell lines compared to adjacent normal tissues. Furthermore, circINTS4 was found to control multiple pathological processes, including cell proliferation and migration, the cell cycle and apoptosis. Regarding the mechanism, circINTS4 directly bound to miR-146b to inhibit its activity of targeting the 3'-UTR of CARMA3 mRNA. In addition, circINTS4 could activate the NF-kB signalling pathway and suppress the P38 MAPK signalling pathway in a CARMA3-mediated manner in BC cells. In summary, the circINTS4/miR-146b/CARMA3 axis might serve as a promising therapeutic target for BC intervention.