Objectives: One of the current challenges in psychiatry is the search for answers on how to effectively manage drug-resistant depression. The occurrence of drug resistance in patients is an indication for the use of electroconvulsive therapy (ECT). This method is highly effective and usually results in relatively quick health improvement. Despite the knowledge of how ECT works, not all of the biological pathways activated during its use have been identified. Hence, based on the neuroinflammatory hypothesis of depression, we investigated the concentration of two opposite-acting adipokines (anti-inflammatory adiponectin and proinflammatory resistin) and BDNF in antidepressant-resistant patients undergoing ECT. Methods: The study group comprised 52 patients hospitalized due to episodes of depression in the course of unipolar and bipolar affective disorder. The serum concentration of adipokines and BDNF was determined before and after the therapeutic intervention using an ELISA method. In the analyses, we also included comparisons considering the type of depression, sex, and achieving remission. Results: Adiponectin, resistin, and BDNF concentrations change after ECT treatment. These changes are correlated with an improvement in the severity of depressive symptoms and are more or less pronounced depending on the type of depression. Conclusions: Although not all observed changes reach statistical significance, adipokines in particular remain exciting candidates for biomarkers in assessing the course of the disease and response to ECT treatment.