Terrence Tergesen graduated with a degree in Architecture at the University of Manitoba in 1958. Before majoring in Architecture, he spent a year studying Fine Arts. Throughout his entire life, Tergesen possessed a passion for design and drawing, which informed his architectural work. In 1962, along with his friends Jim McFeetors and Orest Sedun, Tergesen started an architecture firm. The firm – McFeetors, Tergesen, Sedun – stayed in business for nearly twenty years, after which point Tergesen joined the office LM Architectural Group. Here he continued his work on designs of hospitals, seniors homes and apartment buildings.
Tergesen grew up in Gimli, Manitoba, and enjoyed having a role in the cultural life of the town he adored. In 1979 and 1980 Tergesen served as President of the Icelandic Festival of Manitoba. Proud of his grandfather and father before him, Tergesen maintained an interest in the family business, H.P. Tergesen & Sons, General Merchant. Later in life, Tergesen became a passionate photography and photograph collector. This interest led to his completion of a comprehensive archival project, which was generously donated to the New Iceland Heritage Museum. A collection of photographs telling the story of a unique place and time, and is known as "Terry's Time."