Secondary school students in Erbil City face various stressors and challenges that may impact their mental well-being. This study aimed to assess the knowledge and practical application of psychological first aid (PFA) among these students. This cross-sectional study was conducted from June 10th to June 25th, 2024, in six high schools in Erbil City, Iraq. Participants were selected using a purposive sampling method. Data were collected using two self-structured questionnaires, which included demographic information, a knowledge assessment, and a practical application assessment of PFA. Statistical analysis was performed using SPSS version 28 (IBM Corp., Armonk, NY). Frequency and percentage were used for categorical variables, and mean and standard deviation for quantitative variables. Ordinal regression analyses were conducted to assess the relationships between demographic variables and PFA knowledge and practice. Spearman correlation was used to determine the relationship between knowledge and practice. A p-value of less than 0.05 was considered statistically significant. A total of 412 students were enrolled in the study. The mean scores for knowledge and practice indicated fair levels, with mean scores of 7.66 ± 1.34 for knowledge and 7.01 ± 1.38 for practice. The analysis showed that 11 students (2.7%) had poor knowledge, 161 students (39.1%) had fair knowledge, and 240 students (58.2%) had good knowledge of PFA. In terms of practice, 15 students (3.6%) exhibited poor practice, 237 students (57.6%) demonstrated fair practice, and 160 students (38.8%) showed good practice of PFA. Significant associations were found between several demographic variables and PFA knowledge and practice. Males had higher knowledge scores (estimate = 1.22, 95% CI: 0.20, 2.24, P = 0.02), as did students from families with insufficient monthly income (estimate = 0.91, 95% CI: 0.10, 1.72, P = 0.03) and those residing in urban areas (estimate = 0.83, 95% CI: 0.17, 1.50, P = 0.01). For practice, the occupation of the father was significant, with unemployed fathers associated with lower practice scores (estimate = -1.08, 95% CI: -2.06, -0.09, P = 0.03). The study showed that students had fair knowledge and practice of PFA. To improve these scores, it is recommended that nurses and educators develop targeted interventions and training programs. These should focus on enhancing students' understanding and practical skills in PFA, ensuring they are better equipped to handle psychological distress among their peers.