The purpose of this paper is to explore the association between the term of the auditor-client relationship (i.e., auditor tenure) and future stock price crash risk. Our focus is motivated by extant accounting academic research, anecdotal evidence and the bad news hoarding theory of crash risk. Academic research suggests that potential litigation concerns incentivize auditors to closely monitor clients’ reporting choices that might mask bad news (e.g., Lys and Watts 1994; Heninger 2001; Baron et al. 2001; Kim et al. 2003; Abbott et al. 2006; DeFond et al. 2012).1 This motivation is especially likely to be true of Big 4 auditors that have greater incentives to provide higher-quality audits because their “deep pockets” subject them to more litigation risk (e.g., DeFond and Zhang 2014).2 In contrast, the recent financial crisis has reignited public discussion regarding the willingness of auditors to monitor bad news reporting of clients (PCAOB 2010; Financial Crisis Inquiry Commission 2011). Specifically, a series of recent crisis-related cases challenge the notion that auditors help to prevent managerial bad news hoarding activities in public firms.3 Auditors are alleged in these cases to have turned a blind eye to managerial manipulative practices that hide negative information from the public (e.g., Valukas 2010; Goldfarb 2010; Coffee 2014; Wiggins et al. 2015).4 For example, concerning usage of offbalance sheet devices to mask bad news, Ernst & Young, external auditors for Lehman Brothers Holdings Inc. (Lehman), were accused of failing to “follow professional standards of care with respect to communications with Lehman’s Audit Committee, investigation of a whistleblower claim, and audits and reviews of Lehman’s public filings” (Valukas 2010, 1027). Importantly, Ernst & Young had an extensive long-term relationship with Lehman.5 Such high-profile audit failures tend to elicit a jaundiced view of the auditor-client relationship. Indeed, among other explanations, commentators in the Wall Street Journal blamed the long-running auditor-client relationship between Ernst & Young and Lehman as contributing to weak auditor independence and fostering managerial bad news hoarding (e.g., Westbrook and Katz 2010; Rappaport and Rapoport 2010; Rapoport 2010). In August 2011, the Public Company Accounting Oversight Board (PCAOB) expressed similar concerns by issuing a concept release on auditor independence and rotation (PCAOB 2011a). Despite the concerns above, it is not obvious that a longer auditor-client relationship leads to more managerial bad news hoarding. On one hand, developing client-specific knowledge may be crucial if auditors are to detect and deter bad news hoarding activity by clients. Over time, auditors gain a better understanding of their client’s business and learn more regarding the critical issues that necessitate specific attention (e.g., Knapp 1991; Johnstone et al. 2001; Johnson et al. 2002; PricewaterhouseCoopers 2002; Beck and Wu 2006; PCAOB 2011b; PricewaterhouseCoopers 2013). This “monitoring-by-learning” perspective implies that longer auditor tenure helps to preempt bad news hoarding activities by clients. On the other hand, if a long-run association with the same client reduces auditor independence (e.g., Mautz and Sharaf 1961; U.S. Senate Metcalf Committee Report 1976; Turner 2002; Carey and Simnett 2006; Davis et al. 2009; PCAOB 2011a), auditors with longer tenure may be less vigilant about bad news hoarding activities by their clients.