Psidium guajava (L.) leaves powder was extracted with ethanol and methanol using percolation method. The extracts were tested for antimicrobial activity against clinical isolates of confirmed extended spectrum β-lactamase producing Escherichia coli, Klebsiella pneumoniae and Proteus vulgaris isolates using disc diffusion method. The extracts were further subjected to phytochemical tests using standard procedures. Sensitivity test results showed that ethanol extract of the plant was active against K. pneumoniae and Proteus vulgaris (8mm) but inactive against E. coli at 30μg/disc concentration while methanol extract of the plant was active against Proteus vulgaris isolates (8mm) but inactive against the remaining isolates at 30μg/disc concentration. Both extracts were active against ESBLs producing Proteus isolates with similar zone of inhibition in
response to equal concentration of the extracts. The results of phytochemical screening indicated the presence of alkaloids, reducing sugars, saponins, steroids and tannins in either or both extracts.