Copaiba oil-resin is widely used in traditional medicine due to its anti-inflammatory, healing, and antiseptic activities. This research aims to extract and evaluate the qualitative and quantitative composition of copaiba essential oil from the oil-resin, and test its effects, after incorporation in a gel applied in volunteers with acne, in a double-blind placebo controlled clinical trial. The essential oil was extracted by steam distillation, and purified by freezing to remove the residual remnant water. The density of the essential oil was gravimetrically determined by weighing 1 mL of liquid at 20 degree C. The identification of the essential oil components was carried out through high-resolution gas chromatography analysis, coupled with mass spectrometry. The essential oil has a density of 0.9175 mg/mL and was composed of 48 substances, 14 of which were the major components representing 95.80% of total essential oil composition. Cis-thujopsene was the main component (46.96% of total essential oil composition). The surface affected with acne decreased when treated with placebo (F = 13.931, p = 0.001, r = 0.518; r2 = 0.268), but the linear model could explain only 26.8% of total variance in original data matrix. There was a highly significant decrease in the surface affected with acne in the areas treated with the 1.0% copaiba essential oil preparation (F = 86.494, p = 0.000, r = 0.834; r2 = 0.695).