BACKGROUND: Governments are increasingly reliant on community health workers to undertake health promotion and provide essential curative care. In 2003, the Government of Ethiopia launched the Health Extension Programme and introduced a new cadre, health extension workers (HEWs), to improve access to care in rural communities. In 2013, to inform the government's plans for HEWs to take on an enhanced role in community-based newborn care, a time and motion study was conducted to understand the range of HEW responsibilities and how they allocate their time across health and non-health activities. METHODS: The study was administered in 69 rural kebeles in the Southern Nations Nationalities and People's Region and Oromia Region that were intervention areas of a trial to evaluate a package of community-based interventions for newborns. Over 4 consecutive weeks, HEWs completed a diary and recorded all activities undertaken during each working day. HEWs were also surveyed to collect data on seasonal activities and details of the health post and kebele in which they work. The average proportion of productive time (excluding breaks) that HEWs spent on an activity, at a location, or with a recipient each week, was calculated. RESULTS: The self-reported diary was completed by 131 HEWs. Over the course of a week, HEWs divided their time between the health post (51%) and the community (37%), with the remaining 11% of their time spent elsewhere. Curative health activities represented 16% of HEWs' time each week and 43% of their time was spent on health promotion and prevention. The remaining time included travel, training and supervision, administration, and community meetings. HEWs spent the majority (70%) of their time with individuals, families, and community members. CONCLUSIONS: HEWs have wide-ranging responsibilities for community-based health promotion and curative care. Their workload is diverse and they spend time on activities relating to family health, disease prevention and control, hygiene and sanitation, as well as other community-based activities. Reproductive, maternal, newborn, and child health activities represent a major component of the HEW's work and, as such, they can have a critically important role in improving the health outcomes of mothers and children in Ethiopia.