Objective: To assess the erosive effect of energy drinks (ED) alone and mixed with alcohol on the human enamel surface in vitro. Methods: Twenty non-erupted human third molars were vertically sectioned in half. Specimens were exposed to 5mL of ED plus 5mL of artificial saliva or 5mL of ED plus 5mL of artificial saliva plus 5mL of alcohol (Pisco). Exposure times were set at 30min and 60min. Erosive assessments were made using scanning electron microscopy (SEM) and energy-dispersive x-ray spectroscopy (EDS). The ED analyzed were Mr. Big, Kem Extreme, Red Bull, and Monster Energy. ED pH measurements were performed at 25°C and titration was done with NaOH 0.1mol/L. Results: The pH ranges were: ED alone 2.55 to 3.46, ED mixed with artificial saliva 2.60 to 3.55, ED mixed with Pisco 2.82 to 3.70, and ED mixed with both 2.92 to 3.86. The pH of Pisco was 6.13, and Pisco mixed with artificial saliva had a pH of 6.23. Titration showed a pH range from 3.5 to 5.7. SEM-EDS analysis showed that Mr. Big and Monster led to clear demineralization at 30 min and remineralization at 60m in. Pisco slightly decreased the erosive effect of these ED. Kem Xtreme and Red Bull led to no demineralization in the first hour. Conclusion: According to the pH, acidity and EDS analysis, the ED of the present study likely caused enamel erosion in human teeth surface dependent on exposure time.