The primary purpose of the research was to investigate the effect of psychological safety on the silent behaviour of academic staff with the mediating role of happiness. This research was descriptive-correlational regarding the data collection method. The statistical population was all employees (administrators and teachers) of public schools in Tehran, of whom 373 persons were selected. The questionnaires included a “psychological safety” questionnaire by Edmondson (1999), a researcher-made questionnaire on “silence behaviour” according to the Vakola and Bouradas questionnaire (2005), and “happiness” by Oxford (1990). Descriptive and inferential statistics (Pearson correlation coefficient and structural equations modelling tests) were used to analyse the data. The results showed a positive and significant relationship between psychological safety and the employees’ happiness. Findings of the structural equations modelling indicated that the direct effect of psychological safety on silence was -0.61, and psychological safety with the mediation of happiness reduced to silence by -0.77. It could be concluded from the results of this research that happiness has an important effect on reducing organisational silence, and this research would provide a theoretical reference for managers to take comprehensive measures to improve happiness in the organisation.