In 2021 an adult with mpox clade IIb infection was admitted to a UK teaching hospital within the High Consequence Infectious Diseases (HCID) network 14 days after travelling from Nigeria and 12 days after onset of symptoms. Subsequently two household contacts (one adult and one child) developed confirmed symptomatic mpox infection and were admitted to the same HCID ward for management. Environmental swabs of high touch and low touch surfaces were collected, including sampling before and after terminal decontamination. In total monkeypox virus (MPXV) was detected in 72 of 222 (32.4%) samples collected by qPCR. Of samples collected from rooms occupied by cases with active infection, where both pre- and post-decontamination results were available, 65% of samples were positive pre-decontamination and 5% post-decontamination. Environmental sampling was also conducted in a suite occupied by asymptomatic contacts and a recovered case; 9/43 (20.9%) samples were positive during occupation and prior to decontamination and 1/27(3.7%) positive post- decontamination. There was variation in the proportion of positive environmental swabs pre-decontamination (14-100%) and post- decontamination (0-15%) between cases. Post-decontamination there was a reduction in qPCR positive samples and where samples remained positive the level of nucleic acid detected decreased. Viral isolation was attempted on 13 of 72 qPCR positive samples and viable virus identified in two samples. One of these samples was collected from a suite not occupied by any person with active infection. This study establishes the utility of environmental sampling around mpox cases to measure infection prevention and control measures including the efficacy of cleaning protocols used.