An Imperial decree in July 1899 established Kushiro as an open port for trading with the United States and the United Kingdom.
Kushiro has been an important port because it is more reliably ice-free during winter than alternative Russian Far East warm-water ports such as Petropavlovsk-Kamchatsky or other ports in Hokkaido such as Hakodate, which occasionally do freeze for short periods due to the lower salinity of the Sea of Japan. For this reason, Kushiro was considered a valuable target for the Tsars during the Russo-Japanese Wars, but it only became a really important port during the 1920s with the growth of commercial fishing, for which its reliable freedom from ice reduced costs. Following the Soviet invasion of the Kuril Islands in August 1945, Kushiro was favoured by the Russians as the eastern cornerstone of a border between an American-occupied south and a Soviet-occupied north--coupled with Rumoi as the western cornerstone. However, these plans were declined by President Harry S. Truman.
On October 11, 2005, the town of Akan, from Akan District, and the town of Onbetsu, from Shiranuka District, was merged into Kushiro. The town of Shiranuka now lies between the two sections of Kushiro.
In 2008, the city had an estimated population of 189,539 and a total area of 1,362.75 km2 (526.16 sq mi), giving a population density of 140 persons per km² (363 persons per sq. mi.).
In addition to its port, Kushiro is serviced by Kushiro Airport with flights from Honshu and by the Super Ōzora limited express train service, which runs seven times per day to the main population centres in the west of Hokkaido.
Kushiro was one of the many Japanese cities to receive a Peace Pagoda. Built by the monks and nuns of the Buddhist order Nipponzan Myohoji, it was inaugurated in 1959.
Kushiro was accorded city status on 1 August 1922. It is the sister city of Burnaby, British Columbia; Petropavlovsk-Kamchatsky, Russia; and Kholmsk, Russia.
Kushiro has a humid continental climate (Dfb) but its winter temperatures are less severe than those of inland East Asia at the same latitude. Its port is the most reliably ice-free throughout winter in all of Hokkaido, due to the lack of indentation in the coastline and absence of large inflows of cold fresh water nearby. It is also markedly sunnier than the extremely gloomy Kuril Islands to its north, being sheltered by Hokkaido's mountains from the heavy snowfalls produced on the Sea of Japan side by the Aleutian Low. It receives only a third as much snowfall as Sapporo and almost twice as much sunshine as the Kuril Islands are estimated to.
Ice hockey is one of the most popular winter sports in Kushiro. In addition to several leagues devoted top amateur play of all ages, Kushiro is home to the Asia League Ice Hockey Nippon Paper Cranes, three time Asia League Champions.
Kushiro and many other cities are interested in hosting bandy teams. On January 8 2017, the township of Akan hosted the first national championship, although the size of the field was a smaller version than the official rules for a bandy field.