TNM™ alloys are novel γ-TiAl based alloys which exhibit a high concentration of β-stabilizing elements such as Nb and Mo. Due to the high volume fraction of disordered β-phase these alloys can be hot-die forged under near conventional conditions. In this study, solid-state phase transformations and phase transition temperatures in Ti-(41-45)Al-4Nb-1Mo-0.1B (in at%) alloys were analyzed experimentally and compared to thermodynamic calculations. Results from scanning electron microscopy, conventional and high-energy X-ray diffraction as well as differential scanning calorimetry were used for the characterization of the prevailing phases and phase transformations. For the prediction of phase stabilities and phase transition temperatures thermodynamic calculations were conducted. ThermoCalc® was applied using a commercially available TiAl database. Combining all results a stable as well as a metastable phase diagram for Ti-(41-45)Al-4Nb-1Mo-0.1B alloys is proposed.