Abstract This paper investigates the influence of sentimental noise traders on the security price adjustment. We use De Long et al.'s (1990) definition of noise traders, who falsely believe they have special information, to extend Easley and O'Hara's (1992) seminal model. Our extended model demonstrates the existence of noise traders in the market narrows bid-ask spreads and slows down the speed of price reversion to the fundamental value. Furthermore, the bid-ask spread widens when noise trader sentiment aligns with the market maker's prior beliefs. We show that the market maker's ability to accurately predict noise traders' sentiment is positively related to the quoted bid-ask spread and to the speed of price reversion. We demonstrate that Easley and O'Hara's model is a special case of our model. Their conclusion that time is a factor in the security price adjustment process is strengthened in the presence of the erroneous sentiment of noise traders.