Al-Co-Cr-Fe-Ni alloys have been modeled by computational thermodynamics according to the CALPHAD approach using literature data and results of a few key experiments performed in this work. As a result, an Al-Co-Cr-Fe-Ni thermodynamic database has been developed, based on the thermodynamic assessments of all the binary and ternary subsystems and the addition of a few quaternary interaction parameters. The assessment was supported by ESPEI (Extensible Self-optimizing Phase Equilibria Infrastructure), a tool for thermodynamic database development within the CALPHAD method. Computed phase equilibria in the quinary system are in good agreement with experimental data from the literature and the present experiments.