Background: Migration is a widespread phenomenon globally, often leading to adverse mental health impacts for migrants, particularly children. Such impacts highlight the importance of appropriate non-pharmacological interventions to mitigate these potential negative outcomes. Depression is one of the most prevalent psychological consequences among immigrant children and, therefore, requires focused intervention and treatment. Objectives: This study aimed to evaluate the effectiveness of the modified complicated grief therapy (MCGT) intervention in reducing symptoms of depression in immigrant children. Methods: For this study, 20 Canadian immigrant children were selected using simple random sampling, with ten assigned to the intervention group and 10 to the control group. Depression levels in participants were measured using the Children's Depression Inventory (CDI) self-report questionnaire, which has demonstrated validity and reliability in previous studies. The intervention method, MCGT, was delivered to the intervention group across 12 online sessions via Google Meet, while the control group received no intervention. Depression levels were assessed at three points: Pre-intervention, immediate post-intervention, and one-month post-intervention. Data were analyzed using SPSS version 22, applying relevant statistical tests to compare pre-and post-intervention scores across study groups. Results: The results indicated that of the 20 children selected, 9 (45%) were boys and 11 (55%) were girls, with an average age of 11.7 ± 1.79 years. The mean ages of fathers and mothers were 41.35 ± 4.96 and 37.35 ± 5.04 years, respectively. Findings showed no statistically significant difference in the average depression scores between the control and intervention groups before the intervention (P = 0.561). However, a statistically significant difference was observed in the mean depression scores between the control and intervention groups immediately after the intervention (P = 0.003) and one-month post-intervention (P < 0.001). In the intervention group, the average depression score decreased by 6.5 points immediately after the intervention and by 10.6 points one month later, whereas an increasing trend in depression scores was noted in the control group. Conclusions: Based on the results, the MCGT intervention method is effective and significant in reducing the depression level of immigrant children. Therefore, counselors and psychologists are suggested to use the MCGT intervention method (as a non-drug method) to reduce depression in children.