While living in Paris, the Seagram Company Ltd was planning a new headquarters in New York under her fathers instructions.
During her time in Paris she had come into contact with the newest artistic and architectural movements of the time.
She was vehemently against the building that had already been designed for the plot by Pereira and Luckman Architects.
In an eight-paged letter (dated June 28, 1954) to her father the only 27-year-old Phyllis managed to encourage him to re-think the initial project.
She was given the mandate to find a suitable alternative and after an extended research lasting six weeks Mies van der Rohe was brought forward as the new candidate.
He received the project and became her mentor supporting her in her wish to become an architect.
From 1954-1958 she was immersed in the process of designing and building the Seagram Building on Park Avenue in New York City.
In 1958 she entered the Yale School of Architecture but then changed to the Illinois Institute of Technology, which she felt better suited what she wanted to learn.
1958 was also the year when Mies van der Rohe, who had served as the head of the Department of Architecture at IIT since 1938, resigned from his position.

Lambert later became the consultant to the Seagram Building, entrusted with its maintenance including the supervision and the curation of all exhibitions and collections, until 2000.

After she obtained her master's degree in 1963, her family commissioned her to design an arts center in Montreal to be known as the Saidye Bronfman Centre, in honor of her mother.
Lambert designed a ‘Misian Structure’.

After the demolition of the Van Horne Mansion on Sherbrooke Street in 1973 twenty-three citizen groups formed Sauvons Montréal.
Lambert became one of the advocates in the efforts to revitalize the struggling Shaughnessy Village district.

In 1975, she founded the heritage preservation group Heritage Montreal. (
She served as its first president until 1983.)
Héritage Montréal raised funds so that conservation groups could take action.
Their tools to stop demolition included marching in the streets, publishing ads and booklets and working with residents.
They developed Canada's largest non-profit cooperative housing renovation, Milton-Parc.

Lambert also saved Shaughnessy House from demolition by buying it.
In 1989 the 19th century mansion became part of the Canadian Centre for Architecture (CCA).

She considered investment in renovating low-to medium-income neighbourhoods as important as the conservation of monuments or building anew.
Since 1997 she held the Fonds d’investissement Montréal (FIM).
It achieved in bringing private sector investment to communitarian housing beyond the limits of government programs.

In 1979, she founded the Canadian Centre for Architecture (CCA),  an influential museum and research centre in Montreal's Shaughnessy Village neighbourhood, and donated 750,000 shares of Seagram to help fund the Centre.
It houses extensive collections of architectural drawings, books, photographs, and archival materials.
The centre's utmost priority is the preservation of architectural heritage.

She served on the board of directors of Cemp's subsidiary, Cadillac Fairview for which she later picketed the offices of project developer.
Again she suggested to work with Mies and supported what was to be known as the Toronto-Dominion Centre.

Her work also includes serving as developer on the restoration of the Millennium Biltmore Hotel in Los Angeles by architect Gene Summers.
While living in Paris, the Seagram Company Ltd was planning a new headquarters in New York under her fathers instructions. During her time in Paris she had come into contact with the newest artistic and architectural movements of the time. She was vehemently against the building that had already been designed for the plot by Pereira and Luckman Architects. In an eight-paged letter (dated June 28, 1954) to her father the only 27-year-old Phyllis managed to encourage him to re-think the initial project. She was given the mandate to find a suitable alternative and after an extended research lasting six weeks Mies van der Rohe was brought forward as the new candidate. He received the project and became her mentor supporting her in her wish to become an architect. From 1954-1958 she was immersed in the process of designing and building the Seagram Building on Park Avenue in New York City. In 1958 she entered the Yale School of Architecture but then changed to the Illinois Institute of Technology, which she felt better suited what she wanted to learn. 1958 was also the year when Mies van der Rohe, who had served as the head of the Department of Architecture at IIT since 1938, resigned from his position.
Lambert later became the consultant to the Seagram Building, entrusted with its maintenance including the supervision and the curation of all exhibitions and collections, until 2000.
After she obtained her master's degree in 1963, her family commissioned her to design an arts center in Montreal to be known as the Saidye Bronfman Centre, in honor of her mother. Lambert designed a ‘Misian Structure’.
After the demolition of the Van Horne Mansion on Sherbrooke Street in 1973 twenty-three citizen groups formed Sauvons Montréal. Lambert became one of the advocates in the efforts to revitalize the struggling Shaughnessy Village district.
In 1975, she founded the heritage preservation group Heritage Montreal. (She served as its first president until 1983.) Héritage Montréal raised funds so that conservation groups could take action. Their tools to stop demolition included marching in the streets, publishing ads and booklets and working with residents. They developed Canada's largest non-profit cooperative housing renovation, Milton-Parc.
Lambert also saved Shaughnessy House from demolition by buying it. In 1989 the 19th century mansion became part of the Canadian Centre for Architecture (CCA).
She considered investment in renovating low-to medium-income neighbourhoods as important as the conservation of monuments or building anew. Since 1997 she held the Fonds d’investissement Montréal (FIM). It achieved in bringing private sector investment to communitarian housing beyond the limits of government programs.
In 1979, she founded the Canadian Centre for Architecture (CCA),  an influential museum and research centre in Montreal's Shaughnessy Village neighbourhood, and donated 750,000 shares of Seagram to help fund the Centre. It houses extensive collections of architectural drawings, books, photographs, and archival materials. The centre's utmost priority is the preservation of architectural heritage.
She served on the board of directors of Cemp's subsidiary, Cadillac Fairview for which she later picketed the offices of project developer. Again she suggested to work with Mies and supported what was to be known as the Toronto-Dominion Centre.
Her work also includes serving as developer on the restoration of the Millennium Biltmore Hotel in Los Angeles by architect Gene Summers.
Phyllis Lambert