Abstract Expatriate citizens of countries under authoritarian rule have been increasingly engaging in protest against repression in their home countries. Whether such diaspora protests can boost social uprisings inside authoritarian countries, however, is yet to be analysed. I hypothesise that diaspora protests inspire protest against authoritarian rulers inside the home country by reducing political repression or providing the dissidents with a perception of political opportunity. To test this hypothesis, I use Iran as a case study of an authoritarian regime with a sizeable diaspora and notable protest surges in recent decades. Using daily protest data from 1996 to 2018, results show that protests against the Iranian regime by Iranian expatriates were followed by a significant increase in the chance of protest incidence inside Iran. This association is robust to a variety of modelling specifications and independent of the role of transnational organisational links between activists, which has been documented in the literature previously.