A nanocrystalline Ni material was fabricated by adding a surfactant cetyltrimethylammonium bromide electrolyte during the electrodeposition (ED) process. Significant amounts of dislocations, stacking faults, and twins are present in the as-deposited sample, revealing that the increased internal stress and hardness may result from the present defects during the ED process. This shows a different role of the surfactant, which is commonly considered as a grain refiner.