Long‐range spin ordering has been studied in the quasi‐one‐dimensional antiferromagnet α‐FeC2O4⋅2D2O by neutron diffraction on a powdered sample above and below T N =11.7 K. Data at 14 K show essentially the room‐temperature chemical structure. The space group is C2/c, Z=4, and unit cell dimensions are a=11.700 Å, b=5.568 Å, and c=9.847 Å with β=128.05°. Magnetic peaks appear at T N and data at 10.5 K show doubling of the unit cell along the b direction, the chain axis. The ordered structure belongs to the magnetic space group P 2b 2/n with spins parallel to the b axis. Cancellation of certain interchain interactions gives the structure a pronounced two‐dimensional character. At T 2=9.5 K a discontinuous transition to a second magnetic phase occurs with additional doubling of the unit cell in the a direction. Below T 2 the symmetry of the magnetic structure is reduced to triclinic, P 2s 1̄ with the spins deviating slightly from the b axis.