In the early 1900s, spurred on largely by railroad construction, farming, and the lumber industry, Japanese immigration to Oregon was on the rise. While only twenty-five Japanese lived in Oregon in 1890, by 1900 that number had increased to 2,501, 1,300 in Portland alone. By 1910, there were 3,418 Japanese residents and eighty-three Japanese-operated farms, totaling 4,608 acres, and it was common for those who lived in Portland to own and operate successful mercantile ventures. As Japanese interests in the region increased, so too did the need for organized associations to help foster positive cultural exchange. For over a hundred years, the Japanese Ancestral Society of Portland has operated within the community to just such ends.

Research indicates that the Japanese Ancestral Society can trace its roots to the forming of the Japanese Deliberative Council of Oregon in 1907, which became the Japanese Association of Oregon (Nihon Jin Kai) in 1911. In the decades following their founding, the Japanese Association of Oregon participated in a wide-ranging array of civic activities. They operated a Japanese Free Employment Bureau, established Japanese language classes with the University of Oregon and the YMCA, and hosted several visiting foreign dignitaries. They were known for sending cartloads of fresh produce to charity organizations during the holidays and they even entered an award-winning float in the local Floral Parade. On the whole, Nihon Jin Kai established itself as a virtuous community organization.

However, following the bombing of Pearl Harbor on December 7, 1941, all activities of the “ancestral societies” were suspended and Nihon Jin Kai was shut down. Many leaders of the organization were detained by the FBI. In 1951, the organization was re-activated and changed its name to the Japanese Ancestral Society of Portland (Nikkei Jin Kai).

Today the Japanese Ancestral Society of Portland is a nonprofit organization whose goal is to educate and promote fellowship, and to identify and publicize the achievements of individuals in the Japanese community. The society also sponsors, co-sponsors, or supports events and activities with other Japanese community groups. Ikoi no Kai, for example, is a hot lunch program at the Epworth Methodist Church that provides nutritious meals to the Japanese and Japanese American seniors in Multnomah County. The society also sponsors holiday gift baskets and visits the elderly and the disabled.

Nikkei Jin Kai maintains the Japanese Cemetery in Portland's Rose City Cemetery. An annual Japanese American Graduation Banquet is co-sponsored by the organization to honor high school graduates and to award scholarship funds. Other co-sponsored events are the Nikkei Community Picnic and the Community Mochitsuki, and the traditional New Year’s celebration.

In preserving Japanese culture and language, the Japanese Ancestral Society of Portland works closely with the Office of the Consulate-General of Japan and the Shokookai of Portland, a Japanese business association. The organization supports the consul general’s Japanese Speech Contest for middle and high school students, provides judging assistance for the Toyama Japanese Speech Contest, and supports the Richmond Japanese Language Immersion School.

As of 2010, the Japanese Ancestral Society of Portland had over 280 members carrying on their tradition of community service.