Abstract : This research was planned to assess the different surface treatments effects on the microleakage of the flexible resin at two metals: Co-Cr and Ni-Cr alloys interface. Sixty rectangular samples [50mm x 25mm x 1mm] length, width, thickness respectively. They were prepared with a grid pattern which was formed 50 squares. every sample was divided to experimental half [with treatment] and a control half [without treatment]. There were 2main groups according to the alloy’s kind: 30samples for Cobalt-Chromium alloy and 30samples for Nickel-Chromium alloy. Each main group were further subdivided into 3 subgroups according to the type of surface treatments: fiber laser surface treatment Z-prime plus, or combination of them [fiber laser +Z-prime]. All of them were thermocycle then the test was done. The collected data was analyzed by independent one-way ANOVA, T-test, and LSD-test at a significance level [p-value≤0.05]. A result was showed that the subgroups of combination [fiber laser surface treatment and Z- Prime] for both Co-Cr and Ni-Cr alloys had the least microleakage values, followed by the Z-prime surface treatment alone. The highest value was seen in laser-treated subgroups. Both laser-treated with Z-Prime for two Co-Cr and Ni-Cr alloys revealed the highest reduction in microleakage than other types of surface treatments