Background and Objective: In recent years, there has been a growing interest in the use of dental lasers for treatment of periodontal diseases. The aim of this clinical trial was to evaluate the effect of low level laser therapy (LLLT) as an adjunct to non-surgical periodontal treatment (NSPT). Subjects and methods: All 10 systemically healthy patients who were included in the study were assigned in a split mouth design clinical trial to receive NSPT. One side received LLLT while the other side was not. A diode laser with a wavelength of 850nm-980nm was used and energy output of 2w/ min was applied after periodontal treatment on the first and second days. Plaque index (PI), gingival index (GI), probing depth (PD) and clinical attachment loss (CAL) were recorded at baseline, 1, 3 and 6 months after the treatment. Radiodensitometric analysis was done for both sides at baseline and 6 months. Results: The LLLT sites showed significantly more improvement in gingival index (GI) level compared to the control sites. Highly significant difference between the two sites was observed at 1month while no significant difference was noted at 3 and 6 months. As per the plaque index (PI) there was a significant difference between the two modalities at 1 and 6 months, while no significant difference was noted at 3 months. Analysis of bone density showed significant increase in density in the laser sites and a significant decrease in control sites. Concerning PD and CAL no significant difference was noticed between the two modalities. Conclusion: Combined NSPT and LLLT resulted in significant improvement in bone density but no significant difference was noted in other clinical parameters between the lased and non lased sites.