The mode in which cancer cells migrate away from the primary tumor is not fully understood. In conjunction with intra-vascular cellular migration, we recently proposed extra-vascular migratory metastasis (EVMM) as a means for cancer cells to venture away from the primary tumor via crawling along the abluminal vascular surface. Here, we propose a protocol that builds on a previous in vitro angiogenesis assay. This protocol details a co-culture approach to monitor fluorescence-tagged migrating cancer cells in the presence of vascular structures. This fluorescence based single cell co-culture approach to monitor cancer cell migratory behavior in real time provides a quantitative approach to decipher the cell decision making processes that cancer cells engage in when undergoing phenotypic switching and exhibiting metastasis like dynamics. This assay can also be adapted for high-throughput analysis and for therapeutic screening of cancer cell metastasis targets