Preclinical data have shown that the herbal extract, ALS-L1023, from Melissa officinalis reduces visceral fat and hepatic steatosis. We aimed to assess the safety and efficacy of ALS-L1023 as the treatment of non-alcoholic fatty liver disease (NAFLD). We conducted a 24-week randomized, double-blind, placebo-controlled 2a study in patients with NAFLD (MRI-proton density fat fraction [MRI-PDFF] ≥ 8% and liver fibrosis ≥ 2.5 kPa on MR elastography [MRE]) in Korea. Patients were randomly assigned to 1800 mg ALS-L1023 (n = 19), 1200 mg ALS-L1023 (n = 21), or placebo (n = 17) groups. Efficacy endpoints included changes in liver fat on MRI-PDFF, liver stiffness on MRE, and liver enzymes. For the full analysis set, a relative hepatic fat reduction from baseline was significant in the 1800 mg ALS-L1023 group (−15.0%, p = 0.03). There was a significant reduction in liver stiffness from baseline in the 1200 mg ALS-L1023 group (−10.7%, p = 0.03). Serum alanine aminotransferase decreased by −12.4% in the 1800 mg ALS-L1023 group, −29.8% in the 1200 mg ALS-L1023 group, and −4.9% in the placebo group. ALS-L1023 was well tolerated and there were no differences in the incidence of adverse events among the study groups. ALS-L1023 could reduce hepatic fat content in patients with NAFLD.