| N-acetylcysteine (NAC) is one of the antioxidant supplements which is thought to improve recovery. Existing studies regarding NAC and recovery presented conflicting results. This systematic review and meta-analysis evaluated the existing trials and determined the efficacy of acute and chronic NAC administration on recovery biomarkers. PubMed, Web of Science, and Scopus were searched up to July 2021. The random effects or fixed effects model was applied in the meta-analysis. Sensitivity and subgroup analyses were performed. In case of the presence of publication bias, standard methods were applied. The meta-analysis comprised 37 papers (1,388 participants). All included studies were in English language. Acute NAC administration indicated no significant effects on lactate, pH, VO2, and CPK-MB ([SMD = −0.06 mmol/L; 95% CI: −0.40, 0.28; p = .714], [SMD = 0.17; 95% CI: −0.28, 0.62; p = .454], [SMD = −0.11 L/min; 95% CI: −0.63, 0.41; p = .686], and [SMD = −0.19 units/L; 95% CI: −0.62, 0.24; p = .395]). Additionally, no evidence of significant influence of chronic NAC administration on lactate, pH, VO2, and CK was revealed ([SMD = 0.01 mmol/L; 95% CI: −0.25, 0.27; p = .950], [SMD = −0.51; 95% CI: −1.73, 0.70; p = .424], [SMD = −0.18 L/min; 95% CI: −0.56, 0.20; p = .361], and [SMD = −0.04 units/L; 95% CI: −0.36, 0.29; p = .821]). No considerable effect of NAC on recovery was found. |