This paper presents the first comprehensive estimates of the economic costs experienced by households in the 2011 Greater Bangkok flood. More generally, it contributes to the literature by presenting the first estimates of flood costs based on primary data collected from respondents of flooded homes using in-person interviews. Two rounds of interviews were conducted with 469 households in three of the most heavily affected districts of greater Bangkok. The estimates of economic costs include preventative costs, ex post losses, compensation received, and any new income generated during the flood. Median household economic costs were US$3089, equivalent to about half of annual household expenditures (mean costs were US$5261). Perhaps surprisingly given the depth and duration of the flood, most houses incurred little structural damage (although furniture, appliances, and cars were damaged). Median economic costs to poor and nonpoor households were similar as a percentage of annual household expenditures (53% and 48%, respectively). Compensation payments received from government did little to reduce the total economic losses of the vast majority of households. Two flood-related deaths were reported in our sampleboth in low-income neighborhoods. Overall, ex post damage was the largest component of flood costs (66% of total). These findings are new, important inputs for the evaluation of flood control mitigation and preventive measures that are now under consideration by the Government of Thailand. The paper also illustrates how detailed microeconomic data on household costs can be collected and summarized for policy purposes.