Background:The objective of this study is to test the antibacterial potency and evaluate the possible synergistic effect between aqueous and ethanolic extracts, flower buds and fruits of Capparis spinosa, and between these extracts and antibiotics. Materials and Methods: Antibacterial activity was determined by the plaque microdilution method against seven pathogenic and multiresistant bacteria. Concerning the synergistic effect, between the aqueous and alcoholic extracts of the two organs of this plant, it was carried out according to the "Checkerboard" method. The synergy between the extracts and the antibiotics was estimated by comparing the diameters of the zones of inhibition on solid medium. Results:The extracts showed interesting antibacterial activity with MICs varying from 1.73 ± 0.04 to 66.66 ± 0.00 mg / ml. Both combinations carried between the extracts of flower buds and fruits, ethanolic and aqueous, against Klebsiella pneumoniae and Pseudomonas aeruginosa showed a synergistic effect with ICIF ranging from 0.02 to 0.24. The association between the four extracts and ten antibiotics on the seven strains tested showed an increase in the antibacterial potency of the antibiotic from 11 combinations ranging from 66% to 471%. Conclusion:The present study show that these tested extracts inhibit the growth of Gram-positive and Gram-negative bacteria, which allows us to deduce their broadened spectrum of action and exploit the efficacy of their bioactive molecules as adjuvants to antibiotics.