The aim of the present study was to systematically review the efficacy of low-level laser therapy (LLLT) as an adjunct to scaling and root planing (SRP) vs SRP alone in the treatment of aggressive periodontitis (AgP). The addressed PICO (Population, Interventions, Comparisons and Outcomes) question was: Is LLLT as an adjunct to SRP effective in the treatment of AgP? Electronic databases, including MEDLINE via PubMed, Cochrane Central Register of Controlled Trials and Cochrane Oral Health Group Trials, and EMBASE, were searched until March 2018. Four clinical studies were included. Three studies showed significant improvement in periodontal outcomes among LLLT group compared to SRP alone, whereas only one study showed comparable periodontal outcomes between the adjunctive LLLT and SRP groups at follow up. The overall mean difference for clinical attachment level gain (weighted mean difference [WMD] = -1.69, 95% confidence interval [CI] = -3.46 to 0.07, P < 0.061) was not significant. However, significant difference for probing depth reduction (WMD = -0.95, 95% CI = -1.66 to 0.23, P = 0.009) was noticed between groups at follow up. Whether LLLT as an adjunct to SRP is more effective than SRP alone in the treatment of AgP remains debatable. Further randomized, clinical trials are required with long follow-up periods and standard laser parameters to reach a strong conclusion.