The presented study investigated for the first time the pre-turning performance before the diamond burnishing of AISI 4340 hardened steel under various cutting speeds, feed values, and cutting depths at flood cooling cutting conditions. Multi-objective optimization was con-ducted to obtain an effective pre-turning process regarding total cost and surface character-istics. The results showed that the pre-turning parameters must be optimized to benefit from diamond burnishing effectively. It was also observed that the diamond burnishing could have been more influential on pre-turned specimens with high surface roughness. Under the bohr-oil-added flood-cutting conditions, the average surface roughness and maximum roughness depth improved by 63.4% and 48.5%, respectively. The most influential parameters for average surface roughness and maximum roughness depth were the feed values with 98.2% and 99.3% contribution ratios, respectively. The Bees algorithm optimized the pre-turning parameters in terms of output parameters. The optimum cutting speed, feed values, and cutting depth levels are 264 m/min, 0.1325 mm/rev, and 0.55 mm, respectively.