In an exploratory clinical trial, four male patients diagnosed with major depressive disorder underwent eight weeks of treatment with a device that generates a low-frequency ultralow magnetic field environment (ELF-ELME). An improvement in depressive symptoms was observed, with no adverse effects, among all patients. If the efficacy of the device can be confirmed in larger clinical trials with a control group, this therapy could serve as an alternative treatment for patients who do not want to take antidepressant medications.