Three-dimensional NiFe2O4 nanofibers with tunable morphology were successfully prepared by the electrospinning process and subsequent annealing. Multiparticle-chain NiFe2O4 nanofibers with varying crystallite sizes from 5.3 nm to 30.2 nm and single-particle-chain with crystallite size of 64.5 nm were achieved at 500-800 and 900 degrees C, respectively. The mechanism of the formation of these tailored morphologies and crystallinity was investigated. Magnetic properties were measured by superconducting quantum interference device at room temperature (300 K) and low temperature (10 K). By combining the large crystallite size, high crystallinity, and strong interparticle magnetic interaction, the NiFe2O4 single-particle-chain nanofibers exhibit the highest saturated magnetization (M-s) and coercivity (H-c) at room temperature compared to multiparticle-chain. The results of this study demonstrate that the magnetic properties of NiFe2O4 nanofibers can be tuned from superparamagnetic to soft ferromagnetic when multiparticle-chain with varying crystallite sizes and their ferromagnetic properties can be strongly improved by tuning the fibrous morphology into single-particle-chain, which finds their usefulness in application such as drug delivery, ferrofluid and high-density storage system.