BACKGROUND Nosocomial infection caused by Pseudomonas aeruginosa (P. aeruginosa) is very common, despite the application of various preventive measures in intensive care units (ICUs) leading to increased morbidity, mortality, prolonged hospital stay, and increased treatment cost. OBJECTIVE The aim of the present study is to identify the source of P. aeruginosa infection in patients admitted to tertiary ICU. METHODS From 200 patients selected randomly, appropriate clinical specimens from different sites were collected and processed for the isolation and identification of the nosocomial pathogens. Surveillance samples from environmental sites and hands of nursing staff were also cultured. RESULTS P. aeruginosa was found to be the most common pathogen associated with nosocomial infections accounting for 23.3% of all bacterial isolates from different infection sites in the ICU. Serotyping of the clinical isolates and surveillance sample isolates from nurses' hands showed serotype E as the most common serotype. Other serotypes of P. aeruginosa were isolated from environmental cultures such as sinks, floors, walls, tap water, etc. CONCLUSIONS Study revealed a high prevalence of P. aeruginosa infections in the ICU attributed to cross transmission from patient to patient via hands of the nursing staff. Strict enforcement of infection control protocols is essential to minimize the disease burden.