Aim: this study aimed to examine the clinical and radiographic outcomes of Locator versus bar attachments for immediately loaded implants supporting mandibular overdentures. Materials and methods: Six patients with sufficient bone received upper and lower conventional dentures. After 3 months of adaptation, patients were classified into 2 groups (3 patient/group). All patients received 4 implants in the mandible using computer guided surgery and the flapless surgical approach. Group 1 received locator attachments and group 2 received SFI bar attachment. All implants were immediately loaded by mandibular overdentures. Plaque index, gingival index, probing depth, implant stability, and vertical bone loss were measured for both groups at implant insertion, 3 and 6 months later. Results: implant survival rate was 100% in both groups. Plaque and gingival scores probing depth and vertical bone loss increased significantly with time. Bar attachment recorded higher plaque scores, gingival scores, probing depth and bone loss than Locator attachment after 6 months of denture insertion. Conclusion: Within the limitation of this preliminary study, regarding the small sample size and the short follow-up period, the following conclusion could be drawn: 1) Both SFI bar and locator attachments can be used successfully to immediately load mandibular 4 implant overdentures with excellent survival rate after 6 months follow up period. 2) SFI bar attachments were associated with increased plaque scores, gingival scores, probing depths and marginal bone loss compared to locator attachments.