MoS₂ clusters have been grown on a TiO₂(110) substrate to provide a model surface for better understanding the adsorbate interactions and chemical activity on titania-supported MoS₂ clusters. Scanning tunneling microscopy experiments show that clusters with elongated shapes and flat tops are formed, and the long axes of the clusters have specific orientations with respect to the [001] direction on TiO₂(110). In contrast, deposition of Mo in the absence of H₂S results in a high density of smaller, round clusters that cover the majority of the surface. The morphologies of the MoS₂ clusters do not change after exposure to various gases (D₂, CO, O₂, H₂O, and methanol) in ultrahigh vacuum. However, exposure to higher pressures of O₂, H₂O, or methanol (10 Torr), as well as exposure to air, causes the clusters to disintegrate as Mo in the clusters becomes oxidized. Temperature-programmed desorption studies with CO on the MoS₂ clusters show a distinct desorption peak at 280 K, which is not observed on metallic Mo or titania. Density functional theory calculations suggest that these new adsorption sites for CO are at the edges of the elongated MoS₂ clusters, particularly along the (101̅0) edge containing sulfur vacancy sites.