Endothelial-like differentiation of dendritic cells (DCs) is an interesting and significant phenomenon, which is worth further investigation. Here, we show that the tumor microenvironment derived from the supernatant of the SW620 human colon adenocarcinoma cell line and colon adenocarcinoma tissue homogenate can promote immature DCs (iDCs) to differentiate from the DC pathway toward endothelial cells, while the peri-carcinoma homogenate supernatant does not have this role. Inhibition of angiopoietin-2 (Ang2) in the supernatant by its antibody has no obvious influence on the endothelial-like differentiation. In contrast, inhibition of vascular endothelial growth factor-A (VEGF-A) blocked the differentiation. During the course of differentiation, a sustained activation of ERK1/2 was detected. PD98059 blocked the phosphorylation of ERK1/2 as well as the endothelial-like differentiation of iDCs. Inhibition of VEGF-A also blocked the phosphorylation of ERK1/2. These data suggest that VEGF-A not Ang2 mediates endothelial-like differentiation of iDCs by ERK1/2 signaling in the microenvironment of human colon adenocarcinoma.