The effect of smoking on nonsurgical periodontal treatment (SRP) is known, but the adjunct use of photobiomodulation (PBMT) to SRP has not been fully investigated in smokers. This study aimed to assess the effect of 820 nm diode laser on SRP in smoker/nonsmoker. Sixty patients (smokers/n = 30, nonsmokers/n = 30) were enrolled in this parallel-arm clinical study. All patients were divided into two main groups: SRP and PBMT + SRP. In PMBT + SRP groups, 7.96 J cm(-2) energy was applied by 820nm diode laser at baseline and first, second and third weeks after SRP. Periodontal pocket depth (PPD), gingival index (GI), plaque index (PI) and clinical attachment level (CAL) were recorded, and also gingival crevicular fluid (GCF) samples were collected at baseline and 6w after SRP. Total antioxidant capacity (TAOC) and total oxidative status (TOS) in GCF were analyzed. PBMT + SRP groups showed a statistically significant decrease in PPD and CAL, not in GI and PI compared with SRP alone. There were no statistically significant differences between smokers and nonsmokers in clinical data at six weeks after treatment. Although TAOC levels were increased in PMBT groups, TOS levels were decreased in all groups at the comparison of baseline and 6w after SRP. Adjunct use of 820 nm diode laser on SRP may improve the clinical parameters in smoker or nonsmoker patient with periodontitis.