The company raised $462 million, with Toyota investing around $400 million, according to Reuters.
The latest round values the three-year-old Silicon Valley-based firm at slightly more than $3 billion.
Other investors include Sequoia Capital China and Beijing Kunlun Tech Co.
Reuters reported the funding earlier on Wednesday, citing people familiar with the matter.
Toyota is just one of the latest automakers to pour money into developing self-driving vehicles.
The latest funding will support Pony.ai's future robotaxi operations and technology development, according to Reuters.
Toyota will launch its first vehicle with autonomous highway driving capabilities this year.