The Health Intervention and Technology Assessment Program (HITAP) was established in 2007. This article highlights 15 lessons from over 15 years of experience, noting five achievements about what HITAP has done well, five areas that it is currently working on, and five aims for work in the future. HITAP built capacity for HTA and linked research to policy and practice in Thailand. With collaborators from academic and policy spheres, HITAP has mobilized regional and global support, and developed global public goods to enhance the field of HTA. HITAP's semi-autonomous structure has facilitated these changes, though they have not been without their challenges. HITAP aims to continue its work on HTA for public health interventions and disinvestments, effectively engaging with stakeholders and strategically managing its human resources. Moving forward, HITAP will develop and update global public goods on HTA, work on emerging topics such as early HTA, address issues in digital health, real-world evidence and equity, support HTA development globally, particularly in low-income settings, and seek to engage more effectively with the public. HITAP seeks to learn from its experience and invest in the areas identified so that it can grow sustainably. Its journey may be relevant to other countries and institutions that are interested in developing HTA programs.