This study examines the determinants of Muslim youths’ intention to adopt Cash Waqf Linked Sukuk (CWLS), focusing on the mediating role of Islamic altruism and generational differences between Generation Y and Z. A quantitative research design was employed using an online self-administered questionnaire and purposive sampling. Data were collected from 391 Indonesian Muslim respondents from Generation Y and Z using a five-point Likert-scale instrument, with 21 retained measurement items. Data were analyzed using Partial Least Squares Structural Equation Modeling (PLS-SEM) and Partial Least Squares Multi-Group Analysis (PLS-MGA). The results show that income level (β = 0.568, p < 0.001), religiosity (β = 0.185, p = 0.001), and Islamic altruism (β = 0.147, p = 0.023) significantly predict CWLS adoption intention, whereas Islamic financial literacy has no significant direct effect (β = −0.065, p = 0.181). Islamic altruism significantly mediates the effects of Islamic financial literacy (β = 0.061, p = 0.033), religiosity (β = 0.053, p = 0.027), and income level (β = 0.024, p = 0.046) on intention. PLS-MGA reveals that Islamic financial literacy, religiosity, and Islamic altruism significantly predict intention among Generation Y but not Generation Z, while income level is significant for both groups. These findings highlight the importance of generation-specific strategies for enhancing CWLS adoption among Muslim youth.