Background. Human umbilical cord-derived mesenchymal stem cells (hUC-MSCs) possess great promise as a therapeutic to repair damaged cartilage. Direct intra-articular injection of mesenchymal stem cells has been shown to reduce cartilage damage and is advantageous as surgical implantation and associated side effects can be avoided using this approach. However, the efficacy of stem cell-based therapy for cartilage repair depends highly on the direct interactions of these stem cells with chondrocytes in the joint. In this study, we have carried out an in vitro cell-to-cell contact coculture study with human articular chondrocytes (hACs) and hUC-MSCs, with the goal of this study being to evaluate interactions between hACs and hUC-MSCs. Methods. Low-density monolayer cultures of hUC-MSCs and hACs were mixed at a ratio of 1 : 1 in direct cell-to-cell contact groups. Results were analyzed using quantitative reverse transcription polymerase chain reaction (qRT-PCR), western blot, enzyme-linked immunosorbent assay (ELISA), and immunofluorescence. Results. A mixed coculture of hUC-MSCs and hACs was found to exhibit synergistic interactions with enhanced differentiation of hUC-MSCs and reduced dedifferentiation of chondrocytes. Mixed cultures after 21 days were found to exhibit sufficient chondrogenic induction. Conclusions. The results from this study suggest the presence of mutual effects between hUC-MSCs and hACs even culture at low density and provide further support for the use of intra-articular injection strategies for cartilage defect treatment.