Pressure-composition-isotherms for Ta-Fe-H systems have been investigated in the temperature range 673-873 K. Tantalum-iron alloys (Ta-xFe, x = 0, 1.6 and 3.2 atom % Fe) were prepared by arc melting using high purity elements. The equilibrium solid solubility of hydrogen in the alloys decreases with an increase of iron content. Thermodynamic parameters of the solution process-the Gibb's free energy, enthalpy, and entropy, for each of the solutions have been calculated. The relative partial molar enthalpy becomes less negative with increase in iron content, whereas the entropy values are nearly constant for these alloys. The solubility changes were explained on the basis of change in lattice strain energy of tantalum due to iron addition.