The booklet explains the better management practices (BMP) for producing high-quality genetically improved farmed tilapia (GIFT) monosex seed. These simple and low-cost methods have been tested and proven over five years of research and development in Timor-Leste. The goal is to support the scaling of fish farming to contribute to food and nutrition security. The booklet is intended as a resource for governments, I/NGOs and private sectors involved in tilapia seed production and grow-out systems in the tropics across the Asia-Pacific region. The booklet was developed under the Partnership for Aquaculture Development in Timor-Leste project (2014–2019) funded by the New Zealand Aid Programme. The project is managed by the CGIAR Research Program on Fish Agri-Food Systems led by WorldFish and implemented in collaboration with the Timor-Leste Ministry of Agriculture and Fisheries.