Objectives To perform the polymorphic and physicochemical characterization of the potential anti‐inflammatory drug, eremantholide C (EREC), as well as to evaluate the influence of these characteristics on its biopharmaceutics classification. Methods Eremantholide C was obtained from chloroformic extract of Lychnophora trichocarpha and crystallized in two distinct solvents: chloroform (EREC 1) and ethyl acetate (EREC 2). To evaluate the polymorphism, EREC samples were submitted to melting point, purity, infrared spectroscopy, differential scanning calorimetry (DSC), X‐ray powder diffraction, optical microscopy and scanning electron microscopy analysis. In addition, EREC samples crystallized after intrinsic dissolution study were submitted to DSC and X‐ray powder diffraction analysis. Key findings EREC 1 showed fusion at 234.7–241.6 °C, while EREC 2 showed fusion at 238.6–243.7 °C. No polymorphic transitions were observed during the intrinsic dissolution experiment. A single sharp endothermic peak was obtained for the EREC samples. X‐ray diffraction showed no crystallographic differences between the EREC samples. EREC 1 and EREC 2 showed birefringence under polarized light and indefinite morphology; however, the shape of the crystals was common to the two samples. Conclusions Eremantholide C does not present classical or morphological polymorphism; therefore, there is no influence of crystalline transitions in the solubility and consequently in its biopharmaceutics classification and oral absorption process.