Lu2AlSi2 crystallizes in the orthorhombic Immm space group. The structure is three-dimensional. Lu is bonded in a 10-coordinate geometry to six equivalent Si atoms. All Lu–Si bond lengths are 2.94 Å. Al is bonded in a 12-coordinate geometry to four equivalent Si atoms. All Al–Si bond lengths are 2.60 Å. Si is bonded in a 9-coordinate geometry to six equivalent Lu, two equivalent Al, and one Si atom. The Si–Si bond length is 2.40 Å.