Self-concept is a key factor in any teaching--learning process in pre-service teachers. However, it could be negatively affected by academic stress, which is constituted by stressors, stress symptoms, and coping strategies. The aim of the study was to determine the relationship between academic stress and self-concept in this population. This was a descriptive, correlational, and cross-sectional study. The sample consisted of 1020 university students in education degrees. In relation to sex, it was found that 75.78% were women and 24.21% were men. The following instruments were used: Self-concept Form 5 (AF-5), the Big Five Inventory-44 (BFI-44), and the SISCO Inventory of Academic Stress. The results indicated that academic stress increases and self-concept decreases as studies progress; likewise, most of the students perceived high levels of stress. It was concluded that academic stress is inversely related to self-concept in pre-service teachers, a fact that should be taken into account in their initial training. Social-emotional factors and neuroticism have a decisive influence on the future teachers' academic stress.