Two mononuclear nickel(II) complexes [NiL 1 (NCS) 2 ] (1) and [NiL 2 (NCS) 2 ] (2) and two azido bridged binuclear nickel(II) complexes [Ni2(L1′)2(N3)2(μ-N3)2] (3) and [Ni2(L2′)2(N3)2(μ-N3)2] (4), where L 1 , L 2 , L1′ and L2′ are N,N-diethyl-N′,N′-bis((3,5-dimethyl-1H-pyrazol-1-yl)methyl)ethane-1,2-diamine (L 1 ), N,N-bis((1H-pyrazol-1-yl)methyl)-N′,N′-diethylethane-1,2-diamine (L 2 ), N,N-diethyl-N′-((3,5-dimethyl-1H-pyrazol-1-yl)methyl)ethane-1,2-diamine (L1′) and N-((1H-pyrazol-1-yl)methyl)-N′,N′-diethylethane-1,2-diamine (L2′) have been synthesized and characterized by microanalyses and physico-chemical methods. Single crystal X-ray diffraction analyses revealed that complexes 1 and 2 are mononuclear NCS − containing Ni(II) complex with octahedral geometry and complexes 3 and 4 are end-on (μ-1,1) azido bridged binuclear Ni(II) complexes with distorted octahedral geometry. Variable temperature magnetic studies of the complexes 3 and 4 display ferromagnetic interaction with J values 19 and 32cm −1 , respectively.