The crystal structure and magnetic properties of a LaCo10Al3 intermetallic compound have been investigated by x‐ray powder diffraction and magnetic measurement. The space group of the LaCo10Al3 structure is I4/mcm, which can be derived from the cubic NaZn13‐type structure. Each unit cell contains four formula units of LaCo10Al3. The lattice parameters are a=8.085(1) Å, c=11.624(8) Å, and the calculated density is Dx=7.07(3) g/cm3. In each unit cell, there are five kinds of equivalent positions, i.e., 4a, 16l(1), 16k 16l(2), and 4d, which are occupied by 4La, 16Co(1), 16Co(2), 16(Co+Al) and 4Co(3) atoms, respectively. The tetragonal LaCo10Al3 intermetallic compound is ferromagnetic with a Curie temperature of 840 K. The magnetic moment per Co atom is 0.84μB, which can be explained by the magnetic valence model. © 1996 American Institute of Physics.