The purpose of this study was to evaluate the differentiation potential of human adipose-derived stem cells (hADSCs) into adipocytes by coculturing them with human mature adipocytes. The transwell culture system was utilized for indirect coculture of hADSCs and human mature adipocytes at four different hADSCs-to-mature adipocytes ratios, i.e., 1:5, 1:1, 2:1, and 5:1. After 8 days of coculture, the Oil Red O and Trypan Blue stainings were performed for the evaluation of adipogenic differentiation of hADSCs. In addition, flow cytometric analysis and Hoechst 33342/PI double staining were performed after 20 days of coculture. The Oil Red O and Trypan Blue stainings showed that hADSCs with high viability could not differentiate into mature adipocytes after 8 or 20 days of coculture. However, flow cytometric analysis indicated that CD105 expression of hADSCs decreased after 20 days of coculture. These results indicated that hADSCs cocultured with human adult adipocytes could not successfully differentiate into adipocytes.