Most previous research finds that well-being at work and job performance are in a linear relationship. Audit organizations are a type of highly professional organization. Based on the affective events theory, this study argues that well-being at work can accelerate the improvement of audit performance, so there is actually a curvilinear relationship between well-being at work and audit performance. Besides, auditing is a job that demands highly professional skills and responsibility. This study argues that auditor’s passion for work can strengthen the relationship between well-being at work and audit performance. The subjects for empirical analysis are auditors in a position of in-charge, deputy manager and manager in the Big Four CPA firms in Taiwan. Our empirical evidence confirms that well-being at work and audit performance are in a curvilinear relationship. In addition, the effect of well-being at work on audit performance is greater in the presence of high work passion and will diminish when the passion is low. Based on findings, managerial implications and suggestions for audit organizations are presented.