Endowment or waqf fund education plays a significant role in the higher education institutions (HEI) ecosystem. In addition, the development of endowment funds or waqf in education became one of the main agendas for the Malaysia Higher Education Ministry to sustain the financial stability of the education institution. However, only slight attention was given to the participation of endower among the alumni of private higher education institutions (PHEI). Therefore, this paper aims to investigate the effects of knowledge, altruism, and trust among PHEI alumni on their intention to contribute endowments or waqf. This study applied quantitative approach by distributing questionnaires to PHEI alumni in Selangor. There were 104 questionnaires returned and analysed by using the SmartPLS software. The results indicate that individual altruism and trust are significantly influenced behavioural endowment intention. However, knowledge has no significant influence on the endowment intention among alumni of PHEI. The findings of this study have significantly contributed to the theory and practices to the related parties such as endowment or waqf institutions, Islamic regulatory bodies, and other stakeholders of PHEI, particularly alumni, to promote social responsibility and sustainable education industry in the country.