Due to triacylglycerol (TAG) polymorphism in cocoa butter, processes conditions or storage, chocolate can present a defect called "fat bloom", when the fat liquid fraction migrates to the chocolate surface resulting in a whitish and brittle appearance. The addition of essential oils, rich in monoterpenes, has been studied as an alternative to avoid it. Some theories have been considered to explain this phenomenon but no one elucidated what kind of thermodynamic interactions could rule such an effect. Therefore, this work was aimed at describing the solid-liquid equilibrium (SLE) behavior of monoterpenes + TAG mixtures, in order to comprehend how monoterpenes could affect the solid phase of a fat. Experimental SLE data were measured by differential scanning calorimetry and optical microscopy and also modeled by the SLE theory. Results showed that monoterpenes could promote significant changes in the TAG crystalline habit by forming solid solutions (SS). This profile varied with the composition of TAG and monoterpene. The SS increased the initial fat melting temperature which could partially explain why such compounds improve chocolate quality, mitigating the fat bloom, according literature. The SLE was here a powerful tool for evaluating the effects of addictives in food formulation, which is an inspiration for future works in this field.