PurposeThe readability of annual reports is an important feature that determines the quality of communication between a firm and its stakeholders. Extant literature has demonstrated that readability characteristics of annual reports are crucial in facilitating the investor's ability to process and analyze information, resulting in higher firm performance and lower agency costs. This study examines the relationship between annual report readability, agency costs and the firm performance of listed financial sector companies in Oman.Design/methodology/approachUsing a sample of 150 firm-year observations of listed financial sector companies on the Muscat Securities Market (MSM) over the period 2014 to 2018, a panel regression analysis is used, along with the system generalized method of moments (GMM) estimation to address endogeneity concerns. The readability of annual reports is proxied by the length of the annual report, the Flesch reading ease and the Flesch–Kincaid index.FindingsThe ordinary least squares (OLS) results suggest that readability proxied by the length of the annual report has no significant relationship with agency cost, return on assets (ROA) or stock returns. The OLS results are confirmed through the system GMM estimation model for agency costs, Tobin's Q and stock returns. Easier-to-read annual reports measured by the Flesch reading ease demonstrate high asset utilization ratio and Tobin's Q. These results emphasize Flesch reading ease measure in explaining the economic significance of agency cost and Tobin's Q. In contrast, difficult-to-read annual reports are observed for firms with high ROA.Research limitations/implicationsThe study is limited to the financial sector. Its generalizability could be extended to a similar sector or countries with features similar to Oman. Future studies on readability could be extended to other sectors of Oman, and financial firms with easier-to-read annual reports show a high Tobin's Q, which reflects the confidence of investors in the stock market. These findings may encourage policymakers to regulate the readability features of annual reports and influence the reporting quality of financials and disclosures also including cross-country comparisons.Practical implicationsFinancial firms with easier-to-read annual reports show a high Tobin's Q, which reflects the confidence of investors in the stock market. These findings may encourage policymakers to regulate the readability features of annual reports and influence the reporting quality of financials and disclosures.Originality/valueWhile the study extends prior literature on readability, agency costs and firm performance, it is also one of the first to examine the financial sector of an emerging country, namely, Oman. The study supports the obfuscation hypothesis through the association of readability measure with agency cost. Unlike prior research that has focused on common computational linguistic literature, this study uses three proxies for readability to assess information quality.