The plant Conyza canadensis, which belongs to Asteraceae (Compositae) family and known as Canadian horseweed. It was used as traditional medicine in China, Pakistan, India, and Africa for the treatment of various diseases causing by bacteria, fungi, or viruses. The plant has antimicrobial, antioxidant, anticoagulant, anti-inflammatory, and anticancer pharmacological activity. This study provides the first phytochemical investigation of the plant in Iraq and is concerned with extraction, fractionation, isolation, and purification of some of the important phytochemicals detected in the plant-like phenolic acids, flavonoids, and alkaloids. Also, the literature survey has revealed that the plant has a substantial antimicrobial activity, so it was deemed desirable to make a study for the antimicrobial activity of the plant. The whole plant was collected from Baghdad city / College of Pharmacy/ University of Baghdad farm during July (2020). The aerial parts and roots were washed thoroughly, dried in shade, chopped, pulverized into a coarse powder, and then weighed. The shade-dried crushed plant materials were first defatted by maceration in hexane for 24 h. Then extracted by two extraction methods (hot method using soxhlet apparatus and cold method by maceration in solvent), using 85% aqueous ethanol as solvent extraction, and fractionated by petroleum ether, chloroform, ethyl acetate, and n-butanol. The phytochemical screening of the ethanolic extract from both extraction methods revealed alkaloids, saponin glycosides, coumarins, flavonoids, steroids, phenolic compounds, proteins, anthraquinones, terpenoids, and cardiac glycosides. However, depending on the percentage yields, the hot method yield was better than the cold method, so the extraction method by soxhlet was preferred upon maceration as it gives a higher percentage yield. The petroleum ether, chloroform, and ethyl acetate fractions were analyzed by thin-layer chromatography (TLC) and high-performance liquid chromatography (HPLC) for their steroids, alkaloids, and polyphenolic (phenolic acids and flavonoids) contents, respectively. The different chromatographic results revealed the presence of stigmasterol and β- sitosterol in petroleum ether fraction, harmine alkaloid in chloroform fraction, quercetin, quercitrin, apigenin, p-coumaric acid, and caffeic acid in ethyl acetate fraction of the Iraqi C. canadensis plant. Three polyphenolics compounds (p-coumaric acid, caffeic acid, apigenin) were isolated from ethyl acetate fraction by preparative thin-layer chromatography plates (PLC), and Harmine alkaloid was isolated from chloroform fraction by high-performance liquid chromatography (HPLC) using a fraction collector. The isolated compounds were subjected to various chromatographic and spectral analytical techniques for their identification, such as TLC, FTIR, HPLC, and high-performance thin-layer chromatography (HPTLC). Petroleum ether fraction was analyzed for the detection of coumarins by TLC. One compound was isolated, purified by PLC, symbolized as MS compound, and identified by FTIR and 1H -NMR since there is no standard available for this compound. The isolated MS compound could be pyranocoumarin glycoside. To investigate the essential oil composition of Iraqi C. canadensis, hydrodistillation of fresh aerial part of the plant was done using Clevenger-type apparatus for 3hr. The essential oils components and the hexane fraction obtained by maceration of the plant material in hexane solvent were identified using GC/MS analysis. The results of GC/MS analysis of the essential oil were abundant by hydrocarbon compounds, particularly by sesquiterpene hydrocarbon. This study also involves a preliminary determination of the antimicrobial activity of ethyl acetate fraction of the plant against two Gram-positive bacteria (Staphylococcus aureus and Staphylococcus epidermidis), two Gram-negative bacteria (Escherichia coli and Klebsiella sp.) and one fungi species (Candida albicans) by measuring the inhibition zone diameter around the hole in mm, compared with streptomycin and fluconazole standard drugs for antibacterial and antifungal activity, respectively. The antimicrobial results showed significant antibacterial activity against S.aureus (gram-positive bacteria) and important antifungal activity against Candida albicans. In contrast, no antibacterial activity was demonstrated against the tested gram-negative bacteria. Furthermore, the antibacterial activity exerted against S. epidermidis (gram-positive bacteria) was affected by dilution dimethyl sulfoxide (DMSO).