Introduction: Bacterial adhesion is affected by the surface properties of orthodontic wires, especially surface roughness. A rough surface provides opportunities for bacterial attachment by expanding the surface area leading to more adhesion areas and preventing the displacement of bacterial colonies. Aim of the work: To assess the capability of different orthodontic arch-wires to retain oral biofilm and to correlate the adhesion to surface roughness of the wires. Materials and Methods: Four types of orthodontic arch-wires were used for the study, Nickel-titanium (NiTi), Copper nickel-titanium (Cu-NiTi) , Beta Titanium (TMA ) & Beta III Titanium (CNA) new arch wires and 4 weeks after intraoral usage, were examined for Surface roughness (SR) using an atomic force microscope (AFM). Adhesion of Streptococcus mutans (MS), Staphylococcus aureus (SA), and Candida albicans (CA) were performed using colony count method. Statistically, the following tests were done: analysis of variance, Pearson correlation coefficient test, post hoc Tukey test. Results: The four wire types showed significant increases in SR (P< 0.05) after 4 weeks of intra-oral usage, TMA wires recorded the highest roughness values while the lowest ones were for NiTi wires. Bacterial adhesion was detected on all wires, ANOVA showed significant differences between the wires concerning MS, SA and CA adhesion. A significant positive correlation (P=.001) was observed between bacterial adhesion and surface roughness after intra-oral exposure. Conclusions: Microbial biofilm adhesion was significantly greater in TMA and CNA than NiTi Cu-NiTi arch-wires. The surface roughness of TMA and CNA was greater than NiTi and Cu-NiTI arch-wires. Surface roughness for all the examined the archwires in this study increased after 4 weeks of intraoral exposure. There was a positive correlation between surface roughness and the biofilm adhesion on the different wires.