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Copaifera (Leguminoseae) species produce a commercially interesting oleoresin that displays several biological activities, including antimicrobial and anti‐inflammatory properties. Labdane‐type diterpenes are the main chemical constituents of these oleoresins, and copalic acid is the only compound that has been detected in all Copaifera oleoresins. In this study, we investigate some aspects of the gas‐phase fragmentation reactions involved in the formation of the product ions from the deprotonated compounds (−)‐ent‐copalic acid (1), (−)‐ent‐3β‐hydroxy‐copalic acid (2), (−)‐ent‐3β‐acetoxy‐copalic acid (3), and (−)‐ent‐agathic acid (4) by electrospray ionization tandem mass spectrometry (ESI‐MS/MS) and multiple stage mass spectrometry (MSⁿ). Our results reveal that the product ion with m/z 99 is common to all the analyzed compounds, whereas the product ion with m/z 217 is diagnostic for compounds 2 …