Two new sodium nickel phosphates, Na 5 Ni 2 (PO 4 ) 3 ·H 2 O (I) and Na 6 Ni 2 (PO 4 ) 3 OH (II), have been synthesized hydrothermally and characterized by synchrotron X-ray diffraction, electron diffraction, low-temperature thermodynamic and magnetic measurements, and ab initio calculations. Unlike the majority of Ni 2+ compounds, I and II show predominant ferromagnetic exchange couplings. I crystallizes in the monoclinic space group P2 1 /n (a = 14.0395(4) Å, b = 5.1847(14) Å, c = 16.4739(4) Å, β = 110.4186(14)°) and features chains of ferromagnetically coupled Ni 2+ ions. In II with the orthorhombic space group Pcmb (a = 7.5007(15) Å, b = 21.4661(4) Å, c = 7.1732(15) Å), the ferromagnetically coupled Ni 2+ ions form dimers arranged on a spin ladder. Both compounds represent rare examples of quasi-one-dimensional ferromagnets. Structural features behind this unusual magnetic behavior are discussed.