Across research studies, autistic traits have consistently been found to predict the quality of life (QoL) of autistic adults. However, our understanding of their exact role remains limited, as autistic traits are typically examined as a unitary construct, with their multidimensional nature being largely overlooked. The present study examined the relative contribution of specific autistic trait domains – social anxiety, mentalising difficulties, and sensory reactivity – to QoL in autistic adults. Participants ( N = 300) completed clinically relevant measures of their autistic traits (i.e., RAADS-14) and QoL (i.e., WHOQOL-BREF and ASQoL), and provided socio-demographic details. Results showed that the consistent presence of social anxiety and mentalising difficulties across development, but not sensory reactivity, significantly predicted poorer QoL, even after accounting for one another and potential confounders. Comparing their relative importance, social anxiety emerged as the most dominant predictor of QoL amongst all variables, followed by mentalising difficulties. These findings provide evidence for the divergent contributions of autistic trait domains to QoL, adding nuance to our understanding of factors relating to autistic adults’ QoL. Overall, this study underscores the importance of considering individual differences in autistic trait profiles when designing individualised support programmes, such as prioritising attention to the presence of social anxiety and mentalising difficulties, to enhance the QoL of autistic adults. Lay Abstract Research consistently shows that autistic adults with more autistic traits generally experience poorer quality of life (QoL). However, our understanding of how they exactly link remains limited. This is because overall autistic trait scores are typically examined, even though autistic traits encompass different types of characteristics (e.g., social and non-social). Specifically, it is yet to be determined which particular autistic traits contribute most to QoL differences among autistic adults. To address this question, the present study examined the relative contributions of three specific domains of autistic traits – social anxiety, mentalising difficulties, and sensory reactivity – to QoL in 300 autistic adults, using self-report questionnaires. We found that the extent to which the three domains contributed to QoL differed. The consistent presence of social anxiety and mentalising difficulties across development, but not sensory reactivity, significantly predicted poorer QoL. Further to this, the presence of social anxiety, followed by mentalising difficulties, were the most important predictors of poorer QoL compared to all other variables, including being male, not being in a relationship, and having one or more co-occurring mental health conditions. These findings suggest that individual differences in specific autistic trait domains should be particularly attended to in the design of more tailored, personalised support programmes, given their important influence on one's satisfaction with life. Overall, this study demonstrates that it would be useful to maximise the clinical use of autistic trait measures, such as moving beyond the focus on overall scores, with an aim to effectively enhance the QoL of autistic adults.