A census of the Critically Endangered Bengal Florican Houbaropsis bengalensis was conducted between March and May 2012 on and surrounding the Tonle Sap floodplain in Cambodia, which supports the last extant population of the Indochinese subspecies blandini. We found a decline in the number of displaying males of 44–64% since a comparable estimate from the same sites in 2005 to 2007. The estimated population, including five individuals at one previously unsurveyed site, is now 216 (95% CI 156–275) displaying males, plus potential non-displaying males and an unknown number of females. If numbers continue to be lost at a similar rate, it is possible that blandini would become extinct within 10 years. Although the population faces multiple threats, this critical situation has primarily been caused by the recent, rapid conversion of the florican’s grassland habitat to intensive, industrial-scale, irrigated rice cultivation. To protect the Bengal Florican from extinction in South East Asia, existing Bengal Florican Conservation Areas (BFCAs) need expansion and improvements, including strengthened legal status by prime ministerial sub-decree and better demarcation, patrolling and management. As priorities, both irrigated rice and scrub encroachment within the BFCAs needs to be reversed, local communities better supported, and land outside the BFCAs monitored and strategically managed for florican conservation. Where possible, further BFCAs need to be established. Land purchase may also be an effective conservation measure; leasing land earmarked for cultivation would be cheaper, but less secure.