OBJECTIVES: Major depressive disorder (MDD) in adolescents is associated with an increased risk of suicide, and electroconvulsive therapy (ECT) is an effective treatment for MDD and suicidal ideation. To investigate underlying central mechanisms, this study examined functional connectome topological organization in adolescents with MDD and suicidal ideation prior to and following ECT. METHODS: Resting-state fMRI images were collected from 28 adolescents with MDD and suicidal ideation and 31 demographically similar healthy adolescents. Whole-brain functional networks were constructed and topological metrics were analyzed using graph theory approaches. RESULTS: Prior to ECT, depressed adolescents showed disrupted global and nodal properties, indicating altered functional connectivity. Following ECT, significant reductions in depression and suicidality symptoms were observed, with a 75 % response rate. ECT led to an increase in the small-worldness of the brain network, suggesting restoration of functional connectivity. Significant improvements were seen in nodal properties, particularly in the central executive network. Group-by-time interactions revealed differences between responders and non-responders in nodal degree and efficiency. LIMITATIONS: Larger sample sizes and extended followed-up periods following ECT treatment are needed to further investigate the neural basis of clinical changes. CONCLUSION: The results of this study reveal dynamic changes in brain network topology of adolescents with depression during the course of ECT, and have an advanced understanding of the neurobiological biomarkers associated with the efficacy of ECT treatment.