A series of 8-(1-aryliminoethylidene)quinaldines and the nickel halides thereof were synthesized and characterized, and the molecular structures of two representative nickel complexes were confirmed by single-crystal X-ray diffraction studies. Upon treatment with diethylaluminium chloride (Et₂AlCl), the nickel pro-catalysts exhibited high activity for ethylene oligomerization (1.24–1.83 × 10⁶ g mol⁻¹(Ni) h⁻¹) with good thermal stability at 60 °C under 10 atm of ethylene. The influence of the reaction parameters on the catalytic behaviour was investigated for these nickel-based systems, including variation of Al/Ni molar ratio and reaction temperature. Furthermore, the effect of the ancillary ligand Ph₃P was also probed.