The triacylglycerols (TAGs) containing saturated (Sat) -unsaturated (U) fatty acid moieties (Sat-U mixed acid TAGs) are widely present in most natural fats and employed in many industrial applications. The mixing behavior of different Sat-U mixed acid TAGs acts important roles in the physicochemical properties TAG-based materials. Among the three main mixing states of miscible, eutectic and molecular compound (MC) forming mixtures, fundamental research has been conducted on the MC crystals formed by different Sat-U mixed acid TAGs to understand the structures, phase behavior and crystallization properties. This article reviews recent studies on the complex thermodynamic, kinetic and structural factors that affect the formation of MC crystals in binary and ternary mixtures of Sat-U mixed acid TAGs (SatUSat, SatSatU, USatU and UUSat) through specific molecular interactions among the component TAGs. Furthermore, the application of the MC-forming mixtures containing cacao butter to new types of cocoa butter alternative is reviewed.