We examine the effect of audit committees’ cultural diversity, as measured through ancestral cultural diversity of audit committee members, on firms’ financial reporting quality. We find that audit committee cultural diversity is associated with a lower likelihood of financial accounting restatements. Our results are driven by firms operating in more complex environments, which suggests that audit committee cultural diversity may be particularly important when the firm is inherently complex. We also find that cultural diversity is associated with a lower likelihood of restatements for companies with more powerful CEOs, suggesting that more culturally diverse audit committees are more effective in restraining CEO accounting opportunism. Additionally, we document that audit committee cultural diversity is associated with an array of other measures of higher reporting quality. Our study thus highlights the importance of cultural diversity in audit committee effectiveness.