Dahi is the most popular fermented dairy product of Indo-Pak Subcontinent. It contains a variety of fermenting microorganisms particularly belong to genera of Lactic Acid Bacteria. A lot of research work has been carried out on the isolation of bacteriocin producing strains of Lactic Acid Bacteria from Dahi particularly Lactococcus spp., Lactobacillus spp., Streptococcus spp. etc. However no work has been done regarding isolation and characterization of bacteriocin producing strains of E. faecium from indigenous dahi in Pakistan. Bacteriocin producing strain of E. faecium is first time isolated from dahi in Pakistan. It has been found that the enterocin AJ01 is a stable bacteriocin produced by E. faecium AJ01. It shows good anti-bacterial activity against pathogenic bacteria. It has the potential to be used as natural preservative in food products. This information may be helpful for the biotechnologists and microbiologists for carrying out further research work on the isolation and characterization of E. faecium strains from different indigenous dairy products.