Aims: The objective of this work is to contribute to the valorization of medicinal and aromatic plants of the Ivorian flora. We propose to determine the chemical composition and to evaluate the antioxidant activity by spectrophotometry of the essential oil of Cardiospermum. grandiflorum Sw Study Design: Valorization of aromatic and medicinal plants. Methodology: The technical of steam distillation using a four-compartment stainless steel device was used to extract the essential oil from the plant matrix. The analysis of the essential oils was carried out on a GC chromatograph (7890A, Agilent Technologies) coupled to a mass spectrometer (5975C, Agilent Technologies). The identification of the compounds was carried out by comparison of the retention indices and mass spectra obtained with those from the National Institute of Standards and Technology (NIST) database and from the literature The antioxidant potential of the extracts was evaluated using the Blois method. Results: The essential oil obtained by steaming, with an aromatic odor and pale yellow color has a yield of (0.0045 ± 0.0002)%. Analysis of the chromatogram and mass spectra obtained by GC-MS identified 24 phytocompounds representing 99.45% of the total chemical composition. The chemical composition of EO consists mainly of hydrocarbon sesquiterpenes (97.72%).The major compound is γ-muurolene (46.06%) (A) followed by β-Caryophyllene (24.35%) (B) and γ-elemene (7.07 %). The essential oil extract of C. grandiflorum exhibits low antioxidant activity compared to vitamin C. The IC 50 value of vitamin C is 0.31 µg / mL while that of EO extract of C grandiflorum is 15.1 µg / mL Conclusion: In the present study, we are interested in the valuation of Cardiospermum grandiflorum an aromatic plant used in traditional Ivorian medicine. The yields of essential oil is low.  (24) phytocompounds were identified there. The essential oil has less antioxidant activity than that of vitamin C,