BACKGROUND: Convulsive therapies are often effective for Treatment-Resistant Depression (TRD), although their mechanisms of action are unclear. Increases in Brain-Derived Neurotrophic Factor (BDNF) levels are observed after Electroconvulsive Therapy (ECT), but more recent evidence calls this claim into question. Moreover, Magnetic Seizure Therapy (MST), a new convulsive technique, has not yet been studied regarding possible neurotrophic modulation. METHODS: We performed plasma BDNF measures before and throughout treatment of adult patients (18 to 65 years old) diagnosed with TRD and submitted to treatment with convulsive therapy (ECT or MST) in the arms of the EMCODE project. RESULTS: We enrolled 31 participants (mean age = 38.4 years, SD = 11.88), 14 (45.16%) were submitted to ECT and 17 (54.84%) to MST. Notable improvements in depressive symptoms were observed in both groups, with no significant difference between them (p = 0.1046). Meanwhile, no significant changes in BDNF plasma levels were observed for any technique, pre and post-treatment (MD = -93.01 pg/ml, 95% CI -545.88 to 359.86), or over time (Coefficient = -67.95, SE = 37.75, p = 0.072). CONCLUSION: The findings suggested no significant changes in plasma BDNF following convulsive therapies, challenging the notion of BDNF as a biomarker for treatment-resistant depression.