Abstract: Mobile phones are dispensable accessories in social life and normally they are not cleaned properly. Therefore, they serve as a reservoir of bacteria and may cause nosocomial infections in hospitals. The purpose of this study was to investigate microbiological colonization of mobile phones used by healthcare staffs. The study was carried out collecting swab samples with Cary-Blair transport medium from mobile phones of attending healthcare staffs from different departments of three hospitals in March, 2008. All collected samples were inoculated in 5% sheep blood agar, eosin-methylene blue agar and Sabouraud Dextrose agar. Isolated bacteria were identified using by classic technique and Vitec2 (Biomerieux, France) full automated bacteria identification system. Growth was observed in 65 of collected 106 samples, corresponding to 61.3%. The most frequent bacteria were Staphylococcus epidermidis followed by Staphylococcus aureus, Bacillus sp., Corynebacterium sp. and Escherichia coli, respectively. In conclusion, bacteria were colonized on mobile phones frequently and mobile phones may become reservoir of microorganism for nosocomial infections.