Chemically-modified triglycerides are prepared by reacting epoxidized triglyceride oils with phosphorus-based acid hydroxide or esters. The phosphorus-containing triglyceride derivatives are of the formula: wherein R1″, R2″ and R3″ are independently selected from C3 to C29 aliphatic fatty acid residues, at least one of which comprising one or both of the derivatized methylene groups of the formula: wherein m is 0, 1 or 2, n is 0 or 1, q is 1, 2 or 3, and R and R′ are independently selected from the group consisting of H, straight, branched or cyclic hydrocarbons and substituted hydrocarbons, and aryl groups. The phosphorus-containing triglyceride derivatives so produced have utility as antiwear/antifriction additives for industrial oils and automotive applications.