The current study sets out to explore test anxiety in adolescent students. The effect of sociodemographic variables on test anxiety was controlled for and the relationship between test anxiety and other psychological constructs, such as self-criticism, social anxiety, acceptance and mindfulness, was examined. In addition, the predictive effect/power of these variables was analyzed and a comparative study between high and low test anxiety adolescents was conducted. Participants in this study were 449 high school students, 211 boys and 238 girls, with a mean age of 16.28 years. These participants completed a battery of self-report questionnaires composed by the Portuguese versions of Test Anxiety Inventory (TAI), Child Acceptance and Mindfulness Measure (CAMM), Forms of Self-Criticizing/Attacking and Self-Reassuring Scale (FSCRS), and the Social Anxiety and Avoidance Scale for Adolescents (SAASA). Results showed that gender, self-criticism and competencies for acceptance and mindfulness had a significant and an independent contribution on the prediction of test anxiety. The comparative study revealed that adolescents with high test anxiety score significantly higher in negative forms of self-criticism, social anxiety and lower in self-reassurance, acceptance and mindfulness, when compared to those with low test anxiety. Despite its exploratory nature, the current study adds to the existing knowledge on the influence of psychological processes, such as self-criticism and acceptance, on test anxiety. These findings might constitute a relevant contribution to psychological intervention with adolescents.