Apple was apparently responding to recent newspaper articles reporting allegations of child labor, 24-hour days and unsafe conditions at its Chinese suppliers.
Apple "cares about every worker in its supply chain," Chief Executive Tim Cook said in an e-mail to the company's 60,000 employees.
The New York Times reported at least half of Apple's Asian suppliers have broken at least one part of its conduct code each year since 2007 and have even broken laws in some cases.
Cook's e-mail promised Apple would "continue to dig deeper" into problems in China and it would "undoubtedly find more issues."
"What we will not do, and never have done, is stand still or turn a blind eye to problems in our supply chain," he wrote.
Huge sales of Apple's gadgets have led to increased pressure on the company's suppliers to speed up production, leading to worker suicides, explosions and accidental poisonings, The Daily Telegraph reported.