Neutron diffraction studies of orthorhombic Co311B7O13Br at 293 K and in the temp. range 1.5-30 K reveal a two step onset of magnetic ordering, starting at the 2nd order transition to a weakly ferromagnetic phase at TN = 17.5 K (Neel type) and followed at about T1 = 10.5 K, by a smooth transformation to a three-dimensional canted magnetic structure (magnetic space group Pc'a21' (Sh29101), magnetic modes Cx(++--), Fy(++++), Az(+--+)). The three Co sites display completely different moment values and directions, arising from frustration effects assocd. with the formation of isolated Co3Br groups with a triangular arrangement of the three Co sites.