This study examines the impact of the audit committee's effectiveness and the board of commissioners' composition on the selection of external auditors. The approach used is a quantitative method with logistic regression to analyze the influence of audit committee's effectiveness (measured by scoring) and board of commissioners' composition (consist of the proportion of independent commissioners, gender diversity, proportion of board of commissioners with interlocks, and total of the board members) on the external auditor selection. The results show that the audit committee's effectiveness and proportion of board of commissioners with interlocks has a positive impact towards the selection of Big 4 external auditor); while the presence of women in the board of commissioners has a negative impact. The other variables that have positive impact are firm size and profitability, meanwhile leverage does not have impact on Big 4 external auditor preference. Since the selection of external auditor represent the audit quality, the results from this study has a practical implication on the need to strengthen the corporate governance mechanisms in terms of the characteristics of board of commissioners to enhance the audit quality and hence the quality of financial statements of Indonesian companies.