Background: Despite the high frequency, severity, and effects of cancer-related fatigue (CRF) on the quality of life (QoL) of patients with cancer, limited treatment options are available. The primary objective of this study was to compare the effects of oral Panax ginseng extract (PG) and placebo on CRF. Secondary objectives were to determine the effects of PG on QoL, mood, and function. Methods: In this randomized, double-blind, placebo-controlled study, patients with CRF ≥4/10 on the Edmonton Symptom Assessment System (ESAS) were eligible. Based on a pilot study, we randomized patients to receive either 400 mg of standardized PG twice daily or a matching placebo for 28 days. The primary end point was change in the Functional Assessment of Chronic Illness Therapy-Fatigue (FACIT-F) subscale from baseline to day 29. Results: Of 127 patients, 112 (88.2%) were evaluable. The mean (SD) FACIT-F subscale scores at baseline, day 15, and day 29 were 22.4 (10.1), 29.9 (10.6), and 30.1 (11.6) for PG (P<.001), and 24.0 (9.4), 30.0 (10.1), and 30.4 (11.5) for placebo (P<.001). Mean (SD) improvement in the FACIT-F subscale at day 29 was not significantly different in the PG than in the placebo group (7.5 [12.7] vs 6.5 [9.9]; P=.67). QoL, anxiety, depression, symptoms, and functional scores were not significantly different between the PG and placebo groups. Improvement in the FACIT-F subscale correlated with baseline scores (P=.0005), Hospital Anxiety and Depression Scale results (P=.032), and sex (P=.023). There were fewer any-grade toxicities in the PG versus placebo group (28/63 vs 33/64; P=.024). Conclusions: Both PG and placebo result in significant improvement in CRF. PG was not significantly superior to placebo after 4 weeks of treatment. There is no justification to recommend the use of PG for CRF. Further studies are needed. Trial Registration: ClinicalTrials.gov identifier: NCT01375114.