Performance appraisals serve as crucial mechanisms for evaluating employee performance and informing decisions related to rewards, promotions, and developmental opportunities. However, the process is susceptible to various biases and errors, often stemming from the ethical frameworks guiding raters' judgments. The chapter explores the impact of utilitarianism and deontological ethics on rater's errors in performance appraisals. Utilitarianism, grounded in the principle of maximizing overall utility or outcomes, may lead raters to prioritize the consequences of performance evaluations over adherence to moral rules or principles. This can result in biases such as leniency or severity, where raters manipulate ratings to achieve desired outcomes or organizational goals. Conversely, deontological ethics, which emphasize adherence to moral duties and principles regardless of consequences, may lead to errors such as halo or horns effects, where raters allow a single characteristic to influence their overall evaluation of an employee.