Surface water flooding probability in London is high but little is known about how aware Londoners are of their exposure. 183 online survey responses showed large differences between perceived flood likelihood and modelled flood probability for respondents’ homes (where the latter could be confidently determined - full addresses cannot be collected due to ethical constraints, which limited sample size and representativeness): 54.6 % overestimated their flood likelihood, 19.7 % underestimated, and 25.7 % were accurate. Residents in high flood probability locations underestimated their exposure. Self-reported flood probability knowledge increased perception accuracy. Climate change concern was linked to flood probability overestimation and implementation of risk mitigation actions.