The microRNA miR-19a is closely related to tumor formation and development and is a key oncogene. Previous studies have demonstrated that miR-19a is upregulated in multiple cancer types, including colorectal cancer (CRC). However, most of these experiments were performed in vitro, and consequently, the mechanisms underlying the effects of miR-19a on CRC are still unclear. Therefore, in the present study, we investigated the role of miR-19a in the development of solid CRC tumors. We generated KRAS 3'UTR-Mut by deleting the predicted binding site for miR-19a in KRAS, and observed that the expression of a reporter gene containing the KRAS 3'UTR in HCT116 cells was suppressed by miR-19a, while that of a reporter gene with mutant KRAS 3'UTR was unaffected by miR-19a. We observed that high miR-19a levels reduced KRAS expression. In the tube formation assay, overexpression of miR-19a exhibited anti-angiogenesis effects, which were rescued by KRAS expression. We established a nude mouse xenograft model to investigate the specific role of miR-19a in solid tumors. The results revealed that the sizes of xenograft tumors and density of blood vessels developed from HCT116 cells expressing miR-19a were smaller/lower compared with those of the control. KRAS and VEGFA levels were also reduced. In conclusion, our results revealed that miR-19a overexpression supressed KRAS expression and angiogenesis in CRC, indicating possibilities of using miR-19a in future therapeutic applications.