The ability to notice and reflect on distressing internal experiences from an objective perspective, often called psychological decentering, has been posited to be protective against mental health difficulties. However, little is known about how this skill relates to age across adolescence, its relationship with mental health, and how it may impact key domains such as affective executive control and social cognition. This study analysed a pre-existing dataset including mental health measures and cognitive tasks, administered to adolescents in Greater London and Cambridge (mean age (SD) = 14.4 (1.77) years, N = 553). A self-report index of decentering based on available questionnaire items in the dataset was developed. Multiple linear regression was used to examine associations between decentering and mental health, affective executive control (measured using an affective Stroop Task, affective Working Memory Task, and affective Sustained Attention to Response Task) and social cognition. Higher decentering was significantly associated with lower depression and anxiety scores and higher psychological wellbeing. Results did not indicate significant relationships between decentering, affective executive control and social cognition. Further research is needed to discover cognitive mechanisms associated with this process, which could allow for optimisation of existing psychological therapy and reveal new avenues of intervention.