To enable the sustainable use of their ocean resources, capacity for ocean science and observations is important for every coastal nation. In many developing areas of the world, capability for ocean science and observations is not yet adequate to meet management needs. International organizations have employed a variety of capacity development approaches to assist developing countries in building self-sustaining ocean science and observational communities. This article describes the lessons learned from visiting scientist programs conducted for more than a decade by the Partnership for Observation of the Global Ocean (POGO) and the Scientific Committee on Oceanic Research (SCOR) that dispatched ocean scientists to developing countries to train hundreds of individuals in a variety of ocean science and observation topics and techniques. From these programs, SCOR and POGO have learned that training in-country has multiple benefits to trainees, host institutions, and trainers, benefits that are not achievable when students leave their countries. These benefits include more cost-effective training on issues relevant to the host institutions using locally available technology, as well as the ability to reach a large number of trainees. Lessons learned from the POGO and SCOR programs can be used to inform the future capacity-development activities of POGO and SCOR, as well as other organizations, to improve, enhance, and expand the use of in-country training and mentoring. Such approaches could contribute to the capacity development efforts of the UN Decade of Ocean Science for Sustainable Development.