Background: Noninvasive neurostimulation with transcranial Pulsed Electromagnetic Fields (tPEMF) may be a promising method for treatment resistant depression (TRD). Studies shown substantial improvement of depressive symptoms in patients with TRD, but there is no information on long-term antidepressant effects. The aim of this study was to investigate the short- and long-term efficacy of tPEMF in participants with TRD. Methods: Eligible participants with TRD in this sham-controlled double-blind multicenter trial were randomly assigned to five weeks either daily active or sham tPEMF. Severity of depression and anxiety was assessed preand directly post-treatment and five and fifteen weeks post-treatment. Primary outcome was change on the 17item Hamilton depression rating scale directly post-treatment. Secondary outcome was change on the Hamilton17 during follow-up and change on the Inventory of Depressive Symptomatology Self-Report and the Beck Anxiety Index. Results: Of the 55 included participants, 50 completed the treatment protocol. Depressive symptoms improved over time in both groups. The improvement continued until the last follow-up measure. There was no difference in outcome between the active and the sham group on change in depression post-treatment or on any secondary measure. Conclusion: Treatment with this type of active tPEMF was not superior to sham in patients with TRD. This is in contrast to a previous study using a similar design and power calculation, but a higher magnetic field strength, that reported improvement of depression after treatment with tPEMF compared to sham. An important limitation of our study was the fact that no different dosing regimens were tried.