Background: Angiopoietin-like protein 4 regulates plasma triglyceride metabolism by modulating the activity of lipoprotein lipase. Results: Fatty acids bind tightly to the N-terminal domain of angiopoietin-like protein 4 and reduce its effect on lipoprotein lipase. Conclusion: Fatty acids play a role in modulating the effects of angiopoietin-like protein 4. Significance: A novel mechanism for regulation of the action of angiopoietin-like protein 4 is proposed.