The masticatory muscles may undergo fatigue due to prolonged mouth opening during the endodontic procedures. Low-level laser can be used to treat muscle fatigue due its capacity to produce reactive oxygen species and improve function of mitochondria. Aim: To determine the effectiveness of low-level laser therapy in the management of masticatory muscle fatigue caused after long endodontic procedure under Local anesthesia. MATERIAL AND METHODS: 44 patients complaining of reduced mouth opening and pain while mouth opening, after long endodontic therapy were considered for the study and were randomly allocated into study and control group. In the study group, low-level laser was applied while patients of control group didn't receive any therapy. In the study group, Visual analogue scale (VAS) score of pain was taken after endodontic therapy, immediately after laser therapy and 4 hours after endodontic therapy. Mouth opening of the patients was measured, before and after endodontic procedure and immediately after laser therapy. In the control group, VAS score of pain was recorded immediately after endodontic therapy and 4 hours after endodontic therapy. Statistical analysis used: ANOVA test and un-paired t-test was used for the data analysis. RESULTS: When both groups were compared, a statistically significant (P=0.0000) reduction with fatigue was found. CONCLUSIONS: The low-level laser can be a useful procedure immediately post long endodontic procedure causing masticatory muscle fatigue. Hence, this therapy can be considered as an add-on therapeutic procedure along with prolonged endodontic appointments to relieve the patient from the discomfort. Key words:Muscle fatigue, Masticatory muscles, Low-level laser therapy.