Tết In Seattle (T-I-S) organizes the annual Tết Festival, a free celebration event held at the Seattle Center as part of Seattle Center's Festál world cultural program. The Tết Festival celebrates the cultural roots of Vietnamese-Americans through the celebration of Tết, the Vietnamese Lunar New Year, by presenting, promoting, and providing hands-on experience in the arts, musics, performances, and foods that are unique to Vietnam.

Tết In Seattle is a 501c3 non-profit organization made up of volunteers in its entirety ranging from the members who make up the Executive and Organizing Committees to the operational teams and performers on the festival days. The organization exists only because of the efforts and contributions of numerous Vietnamese and Non-Vietnamese volunteers who are dedicated to promoting and preserving Vietnamese culture and work year round with the Vietnamese community organizations and groups to organize the two-day festival. 

Tết In Seattle was formed in 1996 by four Vietnamese organizations (VSA-UW, Helping Link, Hội Võ Thuật Thiếu Niên Tacoma, and Liên Đoàn Hướng Đạo Việt Hùng) interested in celebrating and preserving traditional Vietnamese culture in Seattle. With this in mind, these groups wanted to organize an event that would unite the Vietnamese community and introduce its unique culture to the greater Seattle metropolitan. The Vietnamese observance of the Lunar New Year, Tết Nguyên Đán, or simply Tết, was the best means to accomplish this endeavor. Tết In Seattle was born and hosted its first Tết Festival in 1997 in collaboration with the Seattle Center's Festál program.

By mid 1998, Tết In Seattle had grown to become an independent organization with an Organizing Committee that was composed of new volunteers and some members from the original four starting organizations acting as individuals rather than as representatives of any group. For the first several years, Tết in Seattle operated as a non-profit organization under the umbrella of the Ethnic Heritage Council (Seattle Center). In early 2002, Tết In Seattle was awarded its own 501c3 status.

Besides throwing the biggest FREE Tết Festival in the Pacific Northwest and perhaps all of North America, TIS also contributes to community service projects and volunteers to help not just in the Vietnamese community but also the greater Seattle Metropolitan service programs.