This study was conducted to investigate the developmental characteristics of adipocytes and to identify selectively white and brown adipocytes through Fourier transform infrared (FTIR) spectroscopy. For the developmental characterization of adipocytes, cells and conditioned media of white and brown adipocytes were respectively collected and analyzed. A higher amide I/amide II ratio was observed in the conditioned medium of brown adipocyte than in that of white adipocyte, indicating differences in secretory protein profiles. In contrast, an amide I/amide II ratio was higher in white adipocytes than in brown adipocytes, and mature adipocytes have higher lipid amounts than pre-adipocytes. Lipid acyl chain length was the longest in white adipocytes. These differences suggested that FTIR spectroscopy can be used to characterize developmental stages and/or types of adipocytes. To identify the possibility of selectively classifying adipose-derived stem cells, FTIR spectroscopy spectra were obtained in cells before/after white/brown adipocyte differentiation using FTIR spectroscopy and then analyzed by the principal component analysis method. All data indicated that the discrimination between adipocytes was possible in the analysis of the infrared spectroscopy spectrum by the principal component analysis technique. This study suggested the possibility of FTIR spectroscopy as a new type of cell sorting system without tagging.