ObjectiveSuicidality is a common and serious symptom of depression and patients with depression and suicidality often respond to electroconvulsive therapy (ECT), but the mechanism of its effect is poorly understood. We used resting-state functional magnetic resonance imaging (rs-fMRI) to explore changes in brain connectivity before and after ECT in depressed patients with suicidality.MethodsTwenty-three depressed patients with suicidality underwent rs-fMRI at baseline and after 8–12 ECT sessions. Thirty-two age-, sex-, and education-matched healthy controls (HCs) underwent rs-fMRI once. We used functional connectivity (FC) analysis to identify brain regions with altered connectivity in patients compared to HCs and assess changes in FC before and after ECT. We also assessed the clinical symptoms using the Hamilton Depression Scale, 17-item (HAMD-17), and Beck Scale for Suicide Ideation (BSSI).ResultsCompared to HCs, at baseline, patients had reduced FC between the left orbitofrontal cortex (OFC_ Ant_L) and left angular gyrus (Angular_L) (t = 3.849, P < 0.05) with OFC_Ant_L as ROI. With left superior frontal gyrus (Frontal_sup_L) as ROI, patients also had reduced FC between Frontal_sup_L and left superior medial frontal gyrus, medial orbital (Frontal_Med_Orb_L) and left precuneus (Precuneus_L) (t = 3.650, P < 0.05), and increased FC between Frontal_sup_L and right middle frontal gyrus (Frontal_Mid_R) (t = -4.220, P < 0.05). After ECT, with Frontal_sup_L as ROI, patients showed increased FC between Frontal_sup_L and Angular_L after ECT (t = -3.982, P < 0.05) and decreased FC between Frontal_sup_L and right superior and inferior parietal gyrus (Parietal_Sup&Inf_R). In ECT responders, the change in FC between Frontal_sup_L and Angular_L was negatively correlated with the change of the score of BSSI (r = -0.645, P = 0.042), and the change in FC between Frontal_sup_L and Parietal_Sup&Inf_R was positively correlated with the change of the score of BSSI (r = 0.714, P = 0.023). There was no correlation between changes in FC with changes in HAMD-17 score (all P > 0.05).ConclusionOur findings suggest that FC between Frontal_sup_L and Angular_L, and FC between Frontal_sup_L and Parietal_Sup&Inf_R may be involved in the mechanisms by which ECT exerts its effects on suicidality in patients with depression. Our findings provide insights into the neural underpinnings of ECT and may inform the development of more targeted novel therapeutic strategies for suicidality.Trial registrationChinese Clinical Trial Registry, ChiCTR2100048182, Registered 04 July 2021, www.chictr.org.cn