Stress is a normal part of adolescence, yet young people differ markedly in their vulnerability or resilience in the face of everyday stressors (Wright, Masten, & Narayan, 2013). Research has begun to investigate whether emotional intelligence (EI), a set of adaptive traits and skills involving the perception, understanding, use, and regulation of emotions (Zeidner & Matthews, 2018), acts as a 'stress buffer', that operates within risk trajectories to safeguard mental health and well-being (e.g., Keefer, Saklofske, & Parker, 2018; Mikolajczak, Petrides, Coumans, & Luminet, 2009). However, there is a pressing need to conduct more process-oriented EI research, especially in adolescent populations (Fiori, 2009; Peña-Sarrionandia, Mikolajczak, & Gross, 2015). This programme of research explores how and when EI, measured as both an ability (AEI), and as a trait (TEI), acts as a potential stress buffer, through direct effects on the stress response, and indirect effects on emotion regulation (ER) mechanisms. Across three studies (total n = 318, age range = 16 - 18 years), the research tests the extent to which EI moderates several ER processes under stress, as identified from Gross' ER framework (1998a; 1998b). These include 'early' effects (e.g., attentional biases), and 'later', more effortful processes (e.g., coping style), in addition to direct moderation of the stress response itself (e.g., psychological and physiological reactivity). EI's effects are examined in the context of both an active stressor (acute psychosocial stress) and a passive stressor (exposure to distressing posts on social media). While findings are mixed, they suggest that EI does sometimes bestow protection for adolescents when faced with stressors, and moderates several processes within response trajectories (notably, attentional deployment and response modulation), beyond the influence of higher-order personality traits and general cognitive ability. However, these effects are context dependent. Specifically, certain facets of TEI appear most useful when adolescents experience acute psychosocial stress, whereas when confronted with highly emotive material on social media, AEI seems more pertinent. The work suggests both the trait and ability approaches to the study of EI offer valuable insight into adolescent adaptation, and represents a positive step forward in our pursuit to understand how EI might lead to positive life outcomes in young people.