The news comes as a shrinking workforce and changing values about work-life balance in Japan have meant companies are increasingly found responsible for workplace-related suicide.
Toyota City's labour standards officials had been investigating the 2017 suicide of a Toyota Motor employee, a spokesman at the automaker confirmed to Reuters.
"It's true that the labour authority determined it was a workplace injury, but we cannot comment further as discussions between representatives are ongoing," the spokesman said.
Daily newspaper Mainichi Shimbun, which was the first to report the officials' conclusion, said that the employee's supervisor had called him an "idiot" said he was "better dead".
The worker committed suicide in a company dormitory at the age of 28, the newspaper reported. The worker's family plans to sue the automaker, the newspaper said.
Labour officials declined to confirm their decision to Reuters, saying they could not comment on individual cases.
Prime Minister Shinzo Abe has been pushing to improve workplace practices in favour of workers' rights, with issues such as parental leave increasingly in the spotlight.
(Reporting by Takashi Umekawa; Editing by Ritsuko Ando and Christopher Cushing)