OXA-48 β-lactamase is one of the several emerging carbapenemases. Pre-2007 reports were almost exclusively from Turkey, but subsequently its distribution has expanded. We report an early and prolonged outbreak in the UK of Klebsiella pneumoniae producing OXA-48 carbapenemase affecting a predominantly renal cohort in a West London hospital. Carbapenemase production was detected by the modified Hodge test, with confirmation by PCR for blaOXA-48. Isolates were typed by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). Risk factors for acquisition were determined. Between January 2008 and April 2010, 20 K. pneumoniae isolates with reduced susceptibility to carbapenems were identified from 13 patients, comprising 12 renal cases and 1 oncology patient; 8 were outpatients and 5 were inpatients; 7 were deemed to be colonised and 6 infected, including 2 with bacteraemia, 1 of whom died. Hodge tests were positive for all isolates and all had blaOXA-48. PFGE showed strain similarity in isolates from nine patients, whereas four patients' isolates were distinct, representing three further PFGE profiles and suggesting horizontal spread of blaOXA-48. Most patients had received antibiotics in the preceding 3 months and all had healthcare contact, but none had recent travel to areas with endemic OXA-48 Enterobacteriaceae. The renal cohort was screened and a prevalence rate of 0.17% was found. Interventions that collectively brought the outbreak under control included strict infection control precautions, screening, improved laboratory detection protocols and antibiotic stewardship rounds.