Jacobson joined the Seattle firm Young Richard Carleton and Detlie (later TRA) in 1955. He rose to become partner and for over 20 years was the firm's Design Director retiring in 1992. He also was for two years with John Carl Warnecke in San Francisco. At times the firm had branch offices in Anchorage, Boston, Denver and Las Vegas. In addition to the United States the firm was involved in the Middle East, Central America and the Pacific region.

Representative of Jacobson's projects with TRA are:

Washington State Convention and Trade Center - Seattle

State of Washington Capitol Campus - Olympia

Highway Department Administration Building

Public Assistance Department Building

King County Aquatics Center - Federal Way, Washington

Albuquerque International Airport - New Mexico

Mahlon Sweet Airport - Eugene, Oregon

Sealaska Corporation Headquarters Building - Juneau, Alaska

University of Washington - Seattle

McCarty Residence Hall

Aerospace Research Laboratory

Hitchcock Hall Biological Sciences Facility

Health Sciences GHI Wings

Washington State University - Pullman

Wegner Hall

Concurrent with his professional practice Jacobson served on the faculty of the Department of Architecture and the Department of Urban Design and Planning at the University of Washington from 1962 until 2000. During this time he offered a graduate and undergraduate design studios to over a thousand students and guided over 150 master's theses.^{[citation needed]} His administrative duties included the founding and direction of the Building Technology and Administration Program as well as the Graduate Program Director for several years in which he reorganized and expanded the Master of Architecture degree program. In addition he had visiting appointments in architecture teaching at The Royal Academy of Fine Arts-Copenhagen, The University of Sydney-Australia, The Tokyo Institute of Technology and The Royal Institute of Technology-Stockholm.

Jacobson has served on the boards of trustees for Pilchuck Glass School, Northwest Seaport, Northwest Trek Foundation, AIA Seattle, Seattle Architectural Foundation, Northwest Institute for Architecture and Urban Studies in Italy and the Seattle Landmark Preservation Board. He also has served as AIA Seattle Senior Council president and as president of the Washington State Council of Architects.

Jacobsohn has been involved in product design including the design of furniture, lighting fixtures, jewelry and serving pieces. These endeavors and his art photography have been exhibited in the Pacific Northwest and in Italy.

Jacobsohn was honored with Knight First Class Order of the White Rose of Finland, the Silver Award from the Finnish Association of Architects, AIA Seattle Medal of Honor, American Institute of Architects Fellowship, Sigma Tau Outstanding Alumnus- WSU, Washington State University Alumni Achievement Award and membership in six university scholastic honorary societies.

• Grant, Hildebrand (2007). Elegant Explorations. Seattle: University of Washington Press. ISBN 978-0-295-98719-4.
• [Who's Who in America] 2009 (63 ed.). Marquis Who's Who. November 14, 2008. ISBN 0-8379-7017-2.
• "Phillip Jacobson FAIA receives WSU Alumni Achievement Award" (PDF) (Press release). Washington State University. Archived from the original (PDF) on March 26, 2012. Retrieved June 27, 2011.
• University of Washington Library - Special Collections. Phillip Jacobson Papers. Accession No. 5265-001. TRA Archives.^{[need quotation to verify]}

• Pacific Coast Architecture Database
• "Guide to the Phillip Jacobson, FAIA, biographical collection 1958-1998, Cage 687" at Washington State University Libraries (finding aid only, no material available online)