Aim: The aim of this research is to evaluate the antimicrobial potential of ethanol and aqueous (hot and cold) extracts of Hibiscus sabdariffa calyces and the survival of spoilage bacteria in water melon juice fortified with the ethanol extract. Materials and Methods: The isolation and identification of spoilage bacteria of water melon juice was carried out using culture dependent method and morphological and biochemical characterization respectively while extraction of phytochemicals was done with reference to standard procedures. The antimicrobial activities of the different solvent extracts were evaluated based on the agar well diffusion method while the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) were carried out using the macro dilution broth method. Results: The results obtained showed that Staphylococcus aureus, Bacillus cereus, Pseudomonas aeruginosa, Klebsiella pneumoniae, Escherichia coli and Proteus vulgaris were isolated as spoilage bacteria of water melon and phytochemical determination using different extracts showed that Ethanol extract contained 1.35 ± 0.5, 1.21 ± 0.3, 0.41 ± 0.1, 1.50 ± 0.2, 2.40 ± 0.0 mg/g of saponin, tannin, alkaloids, phenols and flavonoids respectively while the hot aqueous extract contained 0.2 ± 0.0, 0.79 ± 0.2, 0.27 ± 0.1 and 0.32 ± 0.1mg/g of saponin, tannin, alkaloids and phenol respectively and the cold aqueous extract contained 0.19 ± 0.1, 0.52 ± 0.2, 0.24 ± 0.1, and 0.11 ± 0.1 mg/g of saponin, tannin, alkaloids, phenol respectively while flavonoids was not detected in the hot and cold aqueous extract. The spoilage bacteria were inhibited by the different extracts showing inhibition zones of 15.3 ± 0.2, 14.3 ± 0.6, 10.7 ± 0.4, 11.0 ± 0.0, 10.7 ± 0.1 and 8.3 ± 0.5mm for Staphylococcus aureus, Bacillus cereus, Pseudomonas aeruginosa, Klebsiella pneumoniae, Escherichia coli and Proteus vulgaris at a concentration of 200 mg/ml respectively of Ethanol extract while the hot aqueous extract demonstrated inhibition zones of 10.7 ± 0.4, 11.0 ± 0.1, 9.0 ± 0.0, 6.7 ± 0.6, 7.3 ± 0.2 and 5.0 ± 0.0 mm for Staphylococcus aureus, Bacillus cereus, Pseudomonas aeruginosa, Klebsiella pneumoniae, Escherichia coli and Proteus vulgaris at a concentration of 200 mg/ ml respectively and the cold aqueous extract showed inhibition zones of 6.7 ± 0.3, 6.0 ± 0.0, 4.0 ± 05, 3.7 ± 0.4, 4.3 ± 0.2 and 0.0 ± 0.0 mm for Staphylococcus aureus, Bacillus cereus, Pseudomonas aeruginosa, Klebsiella pneumoniae, Escherichia coli and Proteus vulgaris at a concentration of 200mg/ml respectively which were significantly different (p < 0.05). The MIC values for Staphylococcus aureus, Bacillus cereus, Pseudomonas aeruginosa, Klebsiella pneumoniae, Escherichia coli and Proteus vulgaris ranges from 50 ± 0.4 to100 ± 0.8 mg/ml using ethanol extracts while the MBC value for Staphylococcus aureus, Bacillus cereus, Pseudomonas aeruginosa, Klebsiella pneumoniae, Escherichia coli, Proteus vulgaris using Ethanol extracts was 200 ± 0.9 mg/ml. The hot and cold aqueous did not have values for the MBC.