Numerous studies have indicated that microRNAs (miRNAs) regulate signalling molecules by acting as oncogenes or tumour-suppressor genes in retinoblastoma (RB). Therefore, investigation of the expression pattern, biological roles and associated mechanisms of cancer-related miRNAs in RB may provide novel therapeutic targets for patients with this disease. miRNA-655 (miR-655) has been reported to be aberrantly expressed in many types of cancers. However, the expression pattern, detailed biological function and underlying molecular mechanisms of miR-655 in RB remain to be clarified. Therefore, the aims of the present study were to detect miR-655 in RB, investigate its biological roles in RB and determine the underlying molecular mechanisms. The results of the present study showed that miR-655 was significantly downregulated in RB tissues and cell lines. Overexpression of miR-655 inhibited the proliferation and invasion ability while it increased the apoptosis of RB cells. Additionally, paired box 6 (PAX6) was identified as a direct target of miR-655 in RB. Furthermore, PAX6 was highly expressed in RB tissues and was negatively correlated with miR-655 expression. PAX6 knockdown recapitulated effects similar to those observed following miR-655 overexpression regarding the proliferation, invasion and apoptosis of RB cells. Rescue experiments demonstrated that restoration of PAX6 expression reversed the tumour-suppressing roles of miR-655 in RB cells. Moreover, upregulation of miR-655 reduced activation of the extracellular signal-regulated kinase and p38 mitogen-activated protein kinase signalling pathways in RB cells through PAX6 regulation. Therefore, restoration of miR-655 expression may be a promising therapeutic strategy for treating patients with RB in the future.