Despite accumulating evidence suggesting a critical role of signal transducer and activator of transcription 3 (STAT3) and Survivin in human bladder cancer, the effects of silencing these genes on the proliferation of T24 bladder carcinoma cells remain unknown. Here, we investigated the inhibitory effects of STAT3 or Survivin silencing on the in vitro and in vivo growth of human T24 bladder carcinoma cells. Small interfering RNA (siRNA) vectors targeting STAT3, Survivin, or both genes were designed and synthesized. The recombinant plasmid DNA constructs were confirmed by DNA sequencing. They were then transiently transfected into T24 cells, and the mRNA and protein expressions of STAT3 and Survivin were determined using real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR) and Western blot, respectively. Cell proliferation was evaluated using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The in vivo growth-inhibition effects of the siRNA vectors were assessed using a bladder cancer mouse model. The tumor weight and size was recorded 4 weeks post-inoculation. We successfully synthesized four siRNA vectors targeting STAT3 and four vectors targeting Survivin. The STAT3-3 and Survivin-4 siRNA constructs were most efficient in reducing STAT3 or Survivin expression, respectively. We then constructed a vector containing these two sequences together (STAT3-Survivin siRNA) and found that the single vector efficiently silenced STAT3 and Survivin expression. Moreover, silencing of STAT3 or Survivin significantly suppressed the in vitro and in vivo proliferation of T24 cells compared to the controls (P<0.05). Our findings indicated that the downregulation of STAT3 or Survivin can suppress the proliferation of T24 bladder cancer cells. Moreover, no additive effects were observed when STAT3 and Survivin were knocked down together, suggesting that they work in the same signaling pathway in T24 cells. These results provide valuable insights into understanding the pathways involved during the tumorigenesis of bladder cancer.