Isothermal titration calorimetry (ITC) is a versatile method used to analyze molecule-to-molecule interactions primarily occurring in non-living systems. Here, we successfully applied ITC for the characterization of receptor-ligand interactions in live cells. In this study, CHO cells or those expressing metabotropic glutamate receptor-1α (CHO-mGluR1α) were suspended in low CaCl2 buffered-saline containing protease inhibitors at incremented temperatures and titrated with agonist (DHPG). Under the optimal recording conditions, titration of DHPG produced heat with time constants that differed between wild type- and CHO-mGluR1α cells. Subtraction of these signals revealed mGluR1α-dependent bimodal responses with rapid heat absorption and successive heat production, as suggested by the thermal imaging of metabotropic receptor signaling. Using the titration curve, mGluR1α-DHPG interactions and the number of binding sites per live cell were characterized. This technique is theoretically applicable for other receptor expression models and ligands. This protocol requires a day to complete the pairwise measurements and single subtraction study.