Electroconvulsive therapy (ECT) is considered an effective treatment for pharmacotherapy-resistant severe mental disorders. Catatonia is a complex syndrome characterised by important psychomotor disturbances. Deep vein thrombosis (DVT) and pulmonary embolism (PE) are frequent side effects of prolonged immobility in catatonic patients. Therefore, it is important to resolve the catatonia as soon as possible. ECT is the most effective therapy available and is generally considered a safe procedure. Nevertheless, its use in patients with DVT or PE and anticoagulant treatment remains controversial. We describe a case of a woman in her 40s with a previous diagnosis of bipolar disorder and dysfunctional personality traits. She was hospitalised with persecutory and reference delusions, high emotional lability, anxiety, somatisation and regressive conduct. She later developed catatonic symptoms. No progress was achieved after a month of hospitalisation, despite several pharmacological treatments. She suffered multiple complications of prolonged bedding, such as an extensive DVT of the left common femoral, the external iliac and the common iliac veins. ECT was conducted under treatment with bemiparin. After the third administration, she showed improvement. No major bleeding or PE was developed. The safety of ECT while receiving anticoagulant therapy has been documented, though dosage and type of anticoagulant must be considered. Location of DVT (proximal or distal) may be an important topic to take into account. This report provides further evidence about the efficacy and safety of undergoing ECT in the context of concomitant serious medical conditions, such as DVT and anticoagulant therapy administration.