Background: Central venous catheters are prone to infectious complications, affecting morbidity, mortality and healthcare costs. Polyhexamethylene biguanide-impregnated discs at the catheter insertion site may prevent local and bloodstream infection; however, efficacy has not been established in a critical care setting. Objective: The objective of this study was to pilot test polyhexamethylene biguanide–impregnated discs compared to standard unmedicated dressings for central venous catheter infection prevention in critically ill patients. Methods: This was a single-centre pilot randomised controlled trial. Adults admitted to intensive care requiring a central venous catheter for >72 h were eligible. Patients with a current bloodstream infection, concurrent central venous catheter, chlorhexidine or polyhexamethylene biguanide allergy, or sensitive skin were excluded. Patients were randomised to receive standard central venous catheter dressings with/without polyhexamethylene biguanide discs. Outcome measures: The primary outcome was feasibility, defined by patient eligibility, recruitment, retention, protocol adherence, missing data, and staff satisfaction. Secondary outcomes included: central line–associated infection; primary bloodstream infection; local infection; skin complications; device/dressing dwell time; serious adverse events, and cost-effectiveness. Results: Of 309 patients screened, 80 participants were recruited with 98% (n = 78) receiving an internal jugular catheter which dwelled for a median of 5 days (interquartile range = 4.0, 6.0). Feasibility criteria were predominantly met (recruitment 88%; retention 100%; protocol fidelity 91%); however, eligibility criteria were not met (32%; most commonly owing to short predicted catheter dwell). Staff acceptability criteria were met, with 83% of staff scoring dressing application and removal ≥7 on a numerical rating scale. There were no central line–associated bloodstream infections and no local infections. Insertion site itch occurred in 4% (control [n = 0], intervention [n = 3]) of participants, while 32% (24/76) reported pain, and 46% (35/76) tenderness. Conclusions: Polyhexamethylene biguanide discs appear safe for central venous catheter infection prevention. Feasibility of a large efficacy trial was established with some modifications to screening processes. Large, adequately powered randomised controlled trials are needed to test the infection prevention hypotheses.