<p>This research investigates the differential effects of varying levels of social capital—namely, family, peer, and school/workplace social capital. The study focuses on youth career development competency (i.e., engagement, self-understanding, career and pathway exploration, and planning and career management) as well as psychological well-being (i.e., purpose in life, personal growth, and life satisfaction) of young people with chronic disabling health conditions (YPCDHC) in Hong Kong. Based on a survey of 243 YPCDHC recruited from 24 service units located in different districts of Hong Kong, we conducted ordinary least squares and unconditional quantile regression analyses. The findings support the hypotheses that all three forms of social capital are positively associated with youth career development competency and psychological well-being, although their effects vary across outcome levels. For youth career development competency, peer social capital exhibits a U-shaped effect, being especially influential at both lower and upper quantiles, while school/workplace social capital becomes increasingly impactful toward the upper end of the distribution. Family social capital demonstrates a consistent but modest influence across all quantiles. In terms of psychological well-being, family social capital plays a stronger role at lower quantiles, whereas school/workplace social capital becomes more predictive at higher quantiles. Peer social capital, by contrast, shows relatively weaker and more variable effects. The detailed unconditional quantile regression findings lay the groundwork for advancing theories related to social capital and developmental outcomes in school-to-work transitions of disadvantaged youth. In addition, with our findings differentiating these impacts, this study also has several implications for practice.</p>