As of October 2007, an estimated 12.79 million people live in Tokyo with 8.653 million living within Tokyo's 23 wards. During the daytime, the population swells by over 2.5 million as workers and students commute from adjacent areas. This effect is even more pronounced in the three central wards of Chiyoda, Chūō, and Minato, whose collective population as of the 2005 National Census was 326,000 at night, but 2.4 million during the day. The entire prefecture had 12,790,000 residents in October 2007 (8,653,000 in 23 wards), with an increase of over 3 million in the day. Tokyo is at its highest population ever, while that of the 23 wards peak official count was 8,893,094 in the 1965 Census, with the count dipping below 8 million in the 1995 Census. People continue to move back into the core city as land prices have fallen dramatically.

As of 2005, the most common foreign nationalities found in Tokyo are Chinese (123,661), South Korean (106,697), North Korean (62,000) Filipino (31,077), American (18,848), British (7,696), Brazilian (5,300) & French (3,000).

The 1889 Census recorded 1,389,600 people in Tokyo City, Japan's largest city at the time.