Sacha inchi is cultivated commercially in Thailand for its edible kernels and oil. Highest quality sacha inchi is normally associated with highest oil content. Samples of 3 maturity stages: green, greenish brown, and brown and dry, were collected from 2 different harvests and comparisons were made based on composition and antioxidant analysis. In each harvest, all 3 stages were collected from the Phitsanulok and Chiang Rai provinces. There were 12 samples plus 2 controls. As maturity increased, moisture content of samples decreased, while oil content increased. Oil content ranged from 38.15-48.81 g/100 g. Protein content ranged from 16.23-18.98 g/100 g. Fibre content was 14.50-22.24 g/100 g, ash content was 2.70-3.06 g/100 g, and carbohydrate content was 7.70-19.47 g/100 g. The total phenolic content (TPC) was 103-385 mg/100 g, and antioxidant activity was 9.36-13.72% for DPPH and 5,803.99-10,700 mg Trolox equivalent for FRAP. Average SFA, MUFA, and PUFA contents were 3.35, 4.63, and 30.91 g/100 g, respectively. Most common FA was omega-6 PUFA, followed by omega-3 and omega-9. Omega-6 to omega-3 ratio was 1.12-1.56. Samples with highest oil content were brown and dry samples harvested from Chiang Rai (47.26 g/100 g oil) and Phitsanulok (46.37 g/100 g oil), which were selected to test for amino acids and vitamin E. Nineteen amino acids were detected, with lysine, tyrosine, leucine, and glutamic acid predominant. Vitamin E content was 1.02-1.42 mg/100 g. For highest quality and greatest benefits to health, sacha inchi should be harvested when the shuck is brown and dry.