In May 2025, trade unions alleged that Costco penalised workers in South Korea for participating in lawful strike action and attempting to take public holidays off, including Labour Day and Children’s Day. According to the union, the company rejected holiday requests, recorded absences as strike participation, and issued warning notices to workers involved in industrial action. It was also alleged that Costco retrospectively altered attendance records by introducing a new classification, “non-fulfilment of duty”, which the union described as a form of evidence manipulation aimed at undermining the strike and intimidating workers. The Service Workers’ Union called for an official investigation into what it described as unfair labour practices and employer interference.

The Business and Human Rights Resource Centre approached Costco Korea for a response but did not receive a reply.