Background Transcranial static magnetic field stimulation (tSMS) in humans reduces cortical excitability. Objective The objective of this study was to determine if prolonged tSMS (2 h) could be delivered safely in humans. Safety limits for this technique have not been described. Methods tSMS was applied for 2 h with a cylindric magnet on the occiput of 17 healthy subjects. We assessed tSMS-related safety aspects at tissue level by measuring levels of neuron-specific enolase (NSE, a marker of neuronal damage) and S100 (a marker of glial reactivity and damage). We also included an evaluation of cognitive side effects by using a battery of visuomotor and cognitive tests. Results tSMS did not induce any significant increase in NSE or S100. No cognitive alteration was detected. Conclusions Our data indicate that the application of tSMS is safe in healthy human subjects, at least within these parameters.