ABSTRACT: This article describes a dataset on firm-level corporate governance (CG) mechanisms in the Sultanate of Oman. It incorporates, in cross-sectional time series (pooled panel) data, eleven variables: corporate governance quality, board of directors' quality, audit committee quality, board independence, board expertise, board size, board meetings, audit committee independence, audit committee expertise, audit committee size, and audit committee meetings. The dataset is derived from 1540 firm-year observations for the period 2005 to 2017, excluding financial firms (482) and firms with missing data (29), resulting in a final sample of 1029 firm-year observations. The data were extracted from six sources: OSIRIS database, CG reports, Google, firm's website, directors' websites, and Bloomberg. Scholarly researchers can readily use this dataset as two data types were created to allow individual and composite measurements of corporate governance mechanisms. The individual determinants are: board independence, board expertise, board size, board meetings, audit committee independence, audit committee expertise, audit committee size, and audit committee meetings. The composite measurements are: corporate governance quality, board of directors' quality, and audit committee quality. This dataset could be used for investigating corporate governance mechanisms in different business and market issues.