The present study investigated the possible tumor-suppressing function of microRNA (miR)-612 and the underlying molecular mechanism of its action in bladder cancer in vitro and in vivo. Reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR) was carried out to quantify the expression levels of miR‑612 in bladder cancer tissues and cell lines. The data demonstrated that the level of miR‑612 expression was significantly reduced in bladder cancer tissues and cell lines, as compared with that in non‑cancerous tissues and cells. Reduced miR‑612 expression was associated with advanced tumor, lymph node and metastasis stages, and with distant metastasis of bladder cancer. A functional study revealed that transfection of cells with an miR‑612 mimic suppressed bladder cancer cell growth, colony formation, migration, invasion and epithelial-mesenchymal transition. Bioinformatics analysis identified that miR‑612 targeted the expression of malic enzyme 1 (ME1), and this was confirmed by western blot and luciferase reporter assay results. Furthermore, the ME1 expression levels were inversely associated with miR‑612 expression in bladder cancer tissue specimens. In addition, knockdown of ME1 expression using ME1 siRNA mimicked the effect of ectopic miR‑612 overexpression in bladder cancer cells in terms of tumor cell growth, migration and invasion. By contrast, ME1 overexpression weakened the inhibitory effect of the miR‑612 mimic in bladder cancer cells. In conclusion, the present study demonstrated that miR‑612 may function as a tumor suppressor in bladder cancer by targeting ME1 expression.