Switching between one's own and another person's perspective is a cognitive component of Theory of Mind (ToM) reasoning that is essential for successful social interaction. Computing another's divergent belief independently from one's own perspective poses a particular challenge. Neuroimaging has demonstrated the involvement of the posterior medial prefrontal cortex (pMPFC) in establishing this perspective difference. Here, we transiently interfered with pMPFC activity by repetitive transcranial magnetic stimulation (rTMS) in a sample of young healthy adults. Reaction times of belief judgments in an adapted false belief task were measured after 1Hz rTMS applied via a double-cone coil. This procedure decreased the discrepancy in reaction times between judging another's and one's own belief, irrespective of whether they were incongruent or congruent. The current results suggest that pMPFC inhibition impaired the ability to distinguish the other's from one's own perspective and support the pMPFC's causal role in establishing perspective differences, an essential component of ToM reasoning.