The Al-Y system is reassessed based on a critical literature review involving recently measured phase diagram and thermodynamic data. In the thermodynamic optimization, the liquid phase is described by using a substitutional solution model. Al3Y, AlY, Al2Y3 and AlY2 are modeled as stoichiometric ones. A two-sublattice model (Al,Y)2(Al,Y)1 has been used to describe Al2Y. A set of self-consistent thermodynamic parameters for the Al-Y binary system has been obtained by means of a CALPHAD approach applied to the selected experimental data. The reliable experimental phase diagram data and thermodynamic properties are well reproduced with the optimal thermodynamic parameters. The observed solidification paths for as-cast alloys can also be described reasonably using the present parameters. Significant improvement has been made, compared with previous assessments.