Appreciative joy is one of four immeasurables emphasised in Buddhism. There are similarities and differences between appreciative joy and gratitude, but their combined roles in improving subjective well-being (SWB) are still unclear. This study aimed to investigate the relationship between appreciative joy and gratitude and their contribution to SWB. Study 1 utilised a cross-sectional survey to evaluate the relationships among appreciative joy, gratitude, and SWB. Study 2 used a randomised controlled trial to explore the effects of a four-week appreciative joy meditation (AJM) training and the underlying mechanisms. The results of Study 1 indicated a moderate positive correlation between appreciative joy and gratitude, and gratitude partially mediated the appreciative joy–SWB relationship. Study 2 further supported the idea that AJM training could increase appreciative joy and gratitude at the one-month follow-up. Furthermore, changes in gratitude caused by the intervention were mediated by appreciative joy. However, since SWB significantly improved at post-measures, we cannot conclude that appreciative joy and gratitude mediated the intervention effect on SWB. Our findings expand the underlying mechanisms of appreciative joy beyond interpersonal domains and highlight the importance of gratitude in understanding the effects of the Buddhist four immeasurable meditations.