We have synthesized an unprecedented 3D cyano-bridged Cr-III-Co-II compound that self-assembles into a periodically ordered, homochiral interlocking structure composed of left-handed single helices and right-handed double-helical strands. It displays four-connected 6(4)8(2) chiral networks and exhibits ferromagnetic order below 12 K. The formation of the helical structure results in the creation of helical tubular channels in the crystal.