Purpose This study aims to evaluate the effects of intellectual capital (IC) efficiency and its components on audit fee stickiness (AFS), such as human capital (HC), organisational capital (OC), structural capital (SC) and relational capital (RC). Moreover, the moderating roles of audit industry specialisation (AIS), tenure and auditors’ market concentration are also estimated. Design/methodology/approach This study’s method is descriptive-correlational based on the information disclosed by listed firms on the Tehran Stock Exchange from 2012 to 2018 using 1,316 year-firm. The method used for hypothesis testing is linear regression using panel data. Findings The results show that all the intellectual capital components (ICCs), including HC, SC, OC and RC, negatively impact audit fees (AFS). Further analyses also show that the AIS moderates the relationship between ICCs and AFS. Originality/value This paper is one of the pioneer studies assessing the auditors’ response to the riskless environments driven by existing IC.