Background: Bacterial infections are one of the prominent problems causing death, health troubles and physical disabilities all over the world. Objective: This study was aimed to compare between hot and cold alcoholic extract of Spirulina platensis. Materials and Methods: in regards to antibacterial efficacy against several multidrug-resistant Gram-positive and Gram-negative bacteria, Spirulina was isolated from a freshwater station located in Baghdad, then identified in consideration to molecular analysis and morphologically. algal extracts were prepared using 70% methanol through Soxhlet and maceration extraction methods, antibacterial activity for both algal extracts was carried out by using agar well diffusion assay against several bacteria (Staphylococcus aureus, Streptococcussp., Pseudomonas aeruginosa, Escherichia coli, Klebsiella sp. and Serratia marscesence), also antibiotic sensitivity was determined for five different antibiotics (Gentamycin, levofloxacin, Netilimicin, Meropeneme, Cefixime) against tested bacteria. Results: The results showed that hot methanolic extract gives higher inhibition zones than cold extract. Besides, GC-Mass assessments resulted to identify biologically active chemicals (36 in hot and 6 in cold) as well as many Phyto-compounds within algal extract respectively. Conclusions: hot alcoholic extract of Spirulina platensis a good and safe choice to treat diseases caused by multi drug-resistant human pathogenic bacteria.