ObjectivesKenya has long and porous borders with its neighbouring countries. These regions, predominantly inhabited by highly mobile rural communities with strong cross-border cultural ties, present major challenges in managing movement of people and COVID-19 preventive measures. Our study sought to assess knowledge of COVID-19 prevention behaviours, how these varied by socioeconomic (SEC) factors and the challenges of engagement and implementation, in two border counties of Kenya.MethodsWe conducted a mixed methods study using a household e-survey (Busia, N=294; Mandera, N=288; 57% females, 43% males), and qualitative telephone interviews (N=73: Busia 55; Mandera 18) with policy actors, healthcare workers, truckers and traders, and community members. Interviews were transcribed, English translated and analysed using the framework method. Associations between SEC (wealth quintiles, educational level) and knowledge of COVID-19 preventive behaviours were explored using Poisson regression.ResultsParticipants were mostly educated to primary school level (54.4% Busia, 61.6% Mandera). Knowledge of COVID-19 prevention varied by behaviour: hand washing-86.5%, use of hand sanitiser-74.8%, wearing a face mask-63.1%, covering the mouth when sneezing or coughing-56.3% and social distancing-40.1%. Differences in knowledge by area, educational level and the wealth index were marked, greatest for Mandera, the less educated and the poor. Interviews with stakeholders revealed challenges in health messaging, psychosocial and socioeconomic factors, lack of preparedness for truck border crossings, language barrier, denial and livelihood insecurity as key challenges to engagement with and implementation of COVID-19 prevention behaviours in the border regions.ConclusionThe influence of SEC disparities and border dynamics on knowledge and engagement with COVID-19 prevention behaviours calls for contextually appropriate risk communication strategies that are cognisant of community needs and local patterns of information flow. Coordinating response measures across border points is crucial in winning communities’ trust and maintaining essential economic and social activities.