Crude non-volatile oleoresin from Burseraceae species (breu), a non-timber forest product of the Amazon, still lacks methods for its quality control even though its pharmacological activities have been associated to the major triterpenes α-amyrin (αAA), β-amyrin, α-amyrenone, β-amyrenone and lupeol (LU). Its chemical characterization has usually been determined by gas chromatography (GC) using columns with phases of low polarity, which are ineffective in the separation of αAA and LU. The present study aimed to develop a GC method to characterize and quantify triterpenes in commercial breu with good selectivity and resolution. Columns with phases of different polarity (DB-35, DB-1701, DB-17HT and DB-Innowax) were tested, and DB-17HT separated αAA and LU without signal suppression or high retention of other constituents. This column allowed the quantification of breu triterpenes using flame ionization detection and cholesterol as a reference standard. Good similarity between the calibration curves of cholesterol and αAA was verified. Internal and external standardizations led to different (p < 0.05) quantifications, but the latter showed less deviation (RSD ≤ 3%). This work provides a reproducible GC method for the quality control of commercial breu, clearly evidencing the presence of lupeol and allowing the accurate quantification of major triterpenes.