Crystal engineering of molecular magnetic materials often leads to novel magnetic functionalities. In this study, we synthesized an ionic chain magnet, i.e., [NiII(imi)6]{[NiII(imi)4][WV(CN)8]}2·4H2O (imi = imidazole; NiW) comprising anionic cyanido-bridged [NiII(imi)4WV(CN)8]nn– chains and cationic mononuclear [NiII(imi)6]2+ complexes. Ferromagnetic coupling between NiII and WV with S = 1 and 1/2, respectively, via a bridging cyanido ligand is found within the chain. However, the total magnetization of NiW is canceled out by a notable antiferromagnetic interchain interaction below a Néel temperature of 8.5 K. Such an antiferromagnetic interaction can be overcome by applying an external magnetic field of 0.9 T at 2 K, and a steep spin-flop transition is observed. From a crystal engineering perspective, we attribute this metamagnetic behavior to the isolated [NiII(imi)6]2+ complex that attracts the chains to be close to each other. Additionally, the complex operates as an independent paramagnetic spin source that offers an extra magnetization state of this compound.