Objectives: We examined the determinants that influence the timeliness of audit reports. Methods: We used 532 observations that were collected over four years (2019 - 2022) from 133 Saudi listed firms, which were analysed using ordinary least squares (OLS) regression and relevant statistical tests (e.g. multicollinearity, autocorrelations, R-squared, adjusted R-squared, and F-value tests). Agency theory was used as a theoretical framework to gain insights about the results. Results: Audit firm size and auditee size were significant attributes that affected the timeliness of audit report lag (ARL) among financial and non-financial Saudi listed firms. Conclusion: This study provides useful insights into the determinants of ARL, as well as timely empirical evidence that complements existing literature in terms of relationships between an audit firm’s attributes and the timeliness of financial reporting.