Pacific National Bank v. Mixter was a United States Supreme Court case that addressed the issue of whether a bank could be held liable for the negligence of its employees. The case involved a dispute between Pacific National Bank and Mixter, a customer of the bank. Mixter had deposited a large sum of money with the bank, and the bank had failed to properly safeguard the funds. Mixter sued the bank for negligence, and the bank argued that it could not be held liable for the negligence of its employees. The Supreme Court held that the bank could be held liable for the negligence of its employees. The Court reasoned that the bank had a duty to its customers to exercise reasonable care in safeguarding their funds, and that the bank had failed to do so. The Court also noted that the bank had a duty to its customers to ensure that its employees were properly trained and supervised, and that the bank had failed to do so. The Court concluded that the bank was liable for the negligence of its employees, and that Mixter was entitled to recover damages from the bank.

In Pacific National Bank v. Mixter, the Supreme Court was tasked with determining whether a bank could be held liable for failing to honor an instrument that had been altered without its knowledge or consent. The majority opinion found in favor of the bank and ruled that it could not be held liable because it did not have actual notice of the alteration at the time when it accepted payment on behalf of its customer. Justice Field dissented from this ruling, arguing that banks should bear some responsibility for their customers' losses due to alterations made without their knowledge or consent. He argued that banks are expected to exercise reasonable care in examining instruments presented by customers and should therefore be held accountable if they fail to do so and accept payments on instruments which have been fraudulently altered without their knowledge or consent.