We synthesized SiCN nanowires by a combination of high-energy ball milling and post-heat treatment using high-purity silicon and carbon nanopowders (< 100 nm), and evaluated the effects of process parameters on their structural, chemical, optical properties, photoelectrocatalytic and photocatalytic activities. Cubic SiCN crystal phase with a lattice constant of 4.35 angstrom was observed. The optical bandgap of 2.20 eV was observed with nanowire diameters ranging from 23 nm to 37 nm. The SiCN nanowires showed good photocatalytic activity with the highest degradation percentage of similar to 99% in 40 min for the degradation of Rhodamine B dye under visible light, and a degradation rate of 0.0841 min(-1). The SiCN nanowires showed no significant reduction in photocatalytic activity for five consecutive cycles, indicating that they are extremely stable against organic dyes. The SiCN nanowires were used for photoelectrochemical water splitting and the effect of electrolytes was studied. The highest photocurrent density of 5 x 10(-2) mAcm(-2) vs. Ag/AgCl in 0.1 M KOH solution was achieved owing to the improved visible light collection and electron hole separation. The exchange current density, Tafel slopes, and limiting diffusion current density were found to be 3.17 mAcm(-2), 68.13 mVdec(-1), and 1.54 mAcm(-2), respectively. Further, the specific capacitance of the SiCN nanowires was estimated, obtained of 188 mFcm(-2) at a current density of 5 mAcm(-2).