This study examines the relationship between perceived security and acceptance of online banking with the mediating effect of perceived risk and trust in Internet banking in Iranian customers. Researchers used structural equations model (SEM) to examine their hypotheses and conceptual model. Statistical data were gathered via a questionnaire from 395 randomly selected customers of Bank Saderat Iran in Semnan. Cronbach’s alpha and internal compatibility were used to check the reliability of the questionnaire. The justifiability of the research variables was checked and confirmed using the first- and second-order confirmatory factor analysis. According to the SEM results, the variables of perceived security and trust in Internet banking had a significantly positive impact on the acceptance of online banking. Although perceived risk had no significant impact on the acceptance of online banking, the results showed that perceived risk had a significantly negative impact on trust in Internet banking.