Nzoia River Basin is one of the regions in Kenya that is highly vulnerable to climate change. An understanding of community knowledge and perception on climate change and drinking water supply will provide strategic directions for national and county government policy, adaptation strategies and development of community-based guidelines on climate change. This study assessed community knowledge and perception on climate change and drinking water supply in Nzoia River Basin. A cross-sectional survey design was used. Three counties were randomly selected from the basin for study with Busia representing the lower catchment, Kakamega middle catchment and Trans Nzoia upper catchment. The study was carried out from May, 2017 to September, 2017. Multistage random sampling technique was used to select the 403 households administered with questionnaires. An observation checklist was used by the interviewers to collect household- and community-related information. The study results revealed that the community largely comes from low socio-economic background: only 24 % had post secondary education or higher, the majority were small scale farmers, housewives, casual workers and househelps (58 %), and only 25 % earned a monthly income above Ksh. 20,000 (equivalent to US $200). The majority of the participants 81 % had some knowledge about climate change but 19 % did not. On level of knowledge about climate change, 70% know a little/something about climate change, 21% know nothing about climate change and 9% know a lot about climate change. Majority of respondents, 76% receive climate change news from mass media (radio, newspaper and magazines, television); and 81 % point out that climate change will have public health risks in the community. The knowledge level about climate change in the basin was average. National and county governments should work with the sector stakeholders in the basin to improve community knowledge and perception regarding climate change, drinking water supply and health needs with proper content. The results of this study will go a long way in bridging the gap between policy formulation and building adaptive capacity to climate change in the basin.