The present research was conducted to evaluate the antimicrobial activities of certain selected xeric plants extracts against certain species of bacteria and fungi by minimum inhibitory concentration assay. The selected xerophytes species of District Bannu for minimum inhibitory concentration (MIC) were Calligonum polygonoides, Sueda fruticosa, Peganum harmala and Rosa brunonii. The antimicrobial activities were carried out in laboratory by using of various strains of bacteria and fungi such as Bacillus subtilis, Escherichia coli, Aspergillus niger and Aspergillus flavus. All the extract of the selected plant were found effective against bacteria and fungi except for S. fruticosa in which weak antimicrobial activities were found. Similarly, it was also investigated that C. polygonoides and R. brunonuii have a high potential of antibacterial activities against the pathogens with less MIC (50, 75 µg mL^‑1). In case of antifungal activities the MIC value (50 µg mL^‑1) of R. brunonuii and C. poygonoides, while in S. fruticosa both the activities were recorded weak with high MIC value (150, 200 µg mL^‑1). It was concluded that amongst the elected xeric plants, C. polygonoides and R. brunonuii have strong antibacterial and antifungal activities with lower values of MIC as compared to S. fruticose. Our report also suggested that the selected medicinal plants of district Bannu have potential properties to inhibit bacteria and fungi growth. This is the first report describing the antimicrobial activities of several Mexican medicinal plants used in this study.