Angiogenesis is a necessary step in tumor growth and metastasis. It is well established that the metabolites of omega-6 and omega-3 fatty acids, which must be obtained through the diet and cannot be synthesized de novo in mammals, have differential effects on cellular processes. Omega-6 fatty acid (n-6 FA)-derived metabolites promote angiogenesis by increasing growth factor expression whereas omega-3 fatty acids (n-3 FA) have anti-angiogenic and antitumor properties. However, most studies thus far have failed to account for the role of the n-6 FA/n-3 FA ratio in angiogenesis and instead examined the absolute levels of n-6 and n-3 FA. This review highlights the biochemical interactions between n-6 and n-3 FA and focuses on how the n-6/n-3 FA ratio in tissues modulates tumor angiogenesis. We suggest that future work should consider the n-6/n-3 FA ratio to be a key element in experimental design and analysis. Furthermore, we recommend that clinical interventions should aim to both reduce n-6 metabolites and simultaneously increase n-3 FA intake.