A semi-flexible bipyrimidyl ligand, 5,5′-bipyrimidin (bpym), was used for the self-assembly of a transition metal coordination polymer, resulting in the formation of a nickel(II) compound, [Ni(Br)2(bpym)2]n (1) with a three-dimemsional (3D) structure. Single-crystal X-ray analysis showed that compound 1 crystallizes in the monoclinic space group C2/c and the structure represents a 3D (4,4)-connected bbe topological framework constructed of nickel(II) ions, twisted cis-μ-bpym and planar trans-μ-bpym groups. Magnetic characterization revealed that 1 shows antiferromagnetic coupling between the pyrimidyl-bridged Ni(II) ions along with weak ferromagnetism due to spin canting with a magnetic ordering below Tc = 3.4 K.