Previous studies have established that Th-U alloys up to 20 wt%U have good irradiation stability. To retain or enhance the irradiation stability of Th-U alloys with increase in uranium content, uranium should be stabilised as isotropic γ-U. Molybdenum is one of the most potent stabilizers of γ-U. Although U-Mo system is well studied, scant availability of open literature related to Th-U-Mo system indicates, need for planned studies. In the present study, effect of molybdenum addition on the microstructural evolution and stability of γ-U phase in some selected compositions of Th-30U alloy has been investigated. A pseudo binary phase diagram of Th-Mo at 30 wt%U has been constructed by CALPHAD approach using respective binary interaction parameters. The origin of as cast microstructure is explained with the help of assessed phase diagram. Three different compositions of Th-U-Mo alloy with varying molybdenum content have been evaluated for their potential application as nuclear fuel.