NiFe 2 O 4 composite ceramics reinforced with carbon fibers (C f ), nickel-coated carbon fibers (NiC f ) and ZrO 2 fibers (ZrO 2f ) were fabricated by the conventional high-temperature solid state reaction at 1300°C for 6hs. The effects of the three kinds of fibers on microstructure and mechanical properties of NiFe 2 O 4 composite ceramics were investigated. The fracture surfaces of NiFe 2 O 4 composite ceramics were observed by scanning electron microscopy (SEM). Elemental analysis of micro-structural phases was performed using energy dispersive spectroscopy (EDS), attached with SEM. Flexural strength by three-point bending techniques and fracture toughness were measured. It was found that leaving holes after reactions between the carbon fiber and matrix led to decreased mechanical properties. The ZrO 2f -doped composite had an improved fracture toughness of 3.05±0.1MPam 1/2 compared to NiFe 2 O 4 composite ceramics having 1.91±0.2MPam 1/2 due to fiber debonding, fiber pull-out and fiber bridging as well as microcracking toughening. The results presented here show that ZrO 2f can serve as a potential toughening agent for NiFe 2 O 4 composite ceramics.