The stability and magnetism in fcc single-crystal nickel nanowires with low-index axial direction are studied by first principles methods in this work. For fcc nickel nanowires, it is found that [110] is the most stable direction, while [111] is less stable and [001] the least stable. Nickel nanowires can be described by a simple core-shell model. The core atoms of nanowires have almost the same magnetic moment as in bulk metal. Surface atoms of nickel nanowires have larger atomic magnetic moments in varying degrees related to axial direction. In our calculated nanowires with low-index axial directions, surface atoms in [110] nanowires have lowest magnetic moments while those in [100] nanowires have the largest.