The overall aim of this thesis was to investigate the effectiveness of stress mindset on stress appraisal tendencies and positive and negative affect. Chapter 1 reviews the current literature on stress mindset and stress appraisals, and how they each relate to adaptive and maladaptive outcomes. Chapter 2 set out to investigate the relationships between stress mindset, challenge and threat appraisal tendencies, and positive and negative affect through a cross sectional study. Chapter 2 also investigated whether challenge and threat mediated the relationship between stress mindset and positive and negative affect. Chapter 3 built on Chapter 2’s findings and used an experimental design to investigate the effectiveness of a brief online video intervention in manipulating stress mindset, appraisal tendencies, and positive and negative affect in university students. Chapter 3 also investigated the effectiveness of the intervention on challenge and threat appraisals, positive and negative affect and the interpretation of anxiety in relation to an upcoming assessment period. Chapter 4 discusses the collective results of both Chapter 2 and 3 and suggests avenues for future research.