The new company will be launched by March 2025 and equally owned by the two firms, Yomiuri reported.
Nikkei reported in July that Mitsubishi Motors was set to join an alliance between Honda Motor and Nissan Motor, creating a tie-up between automakers with combined sales of more than 8 million vehicles.
The push comes as Nissan, Japan's third biggest automaker, has been steadily losing market share in its two largest markets, the United States and China, which together accounted for half of its global sales in the year to March.