Seidler designed about 119 buildings (96 of which were in his home state of New South Wales) but some have since been demolished or altered in a non-Seidler manner, and he received much recognition for his contribution to the architecture of Australia.

He attended Harvard Graduate School of Design under Walter Gropius and Marcel Breuer on a scholarship in 1945/46,[7] and during the university winter (Christmas) inter-semester approximate four weeks break Seidler worked with Alvar Aalto in Boston drawing up plans for the Baker dormitory at MIT.

He then studied visual aesthetics at Black Mountain College under the painter Josef Albers in mid 1946 for the US summer.

[6] For almost 2 months from shortly after 20 April to early June 1948, Seidler also worked in Rio de Janeiro with the architect Oscar Niemeyer.

Seidler arrived in Sydney on (likely) 20 June 1948 (which was a few days before his 25th birthday), with no intention to remain in Australia, but to stay only until the house was finished.

This project was the first completely modern domestic residence to fully express the philosophy and visual language of the Bauhaus in Australia and won the Sulman Award of 1951.

The design introduced the concept of a large public open plaza and prominent artworks to office towers in Australia.

In 1984 he became the first Australian to be elected a member of the Académie d'architecture, Paris and in 1987 was made a Companion of the Order of Australia, an honour which he accepted in his trademark suit and bowtie.

His work is widely recognised as an original and intensely creative contribution to the architecture of the second half of the 20th century.Harry Seidler became a Canadian citizen when he was studying in the USA in late 1945.

[citation needed] Seidler enjoyed photographing architecture around the world and some of these are documented in his photography book The Grand Tour.

[15] She co-designed the Harry & Penelope Seidler House in Killara (suburb of Sydney) which won the NSW Wilkinson award of 1967.

[21] Upon celebrating 50 years of architectural practice in Australia, Seidler noted that developments in building technology allowed for more richness of form in his then soon-to-be completed Horizon apartment tower: "I could not have built Horizon twenty years ago...in earlier building technology (the way one could) span distances, it was very limited.

Seidler's designs from 1969 onwards often displayed opposing negative and positive quarter-circle curves (e.g. retaining garden walls of Pettit & Sevitt exhibition house, Westleigh, 1969, and Condominium Apartments, Acapulco 1969–70).

Seidler articulated the visual-spatial design principle of modern architecture being "dissolution of conventional solidity" and inter-connecting spatial vistas.

Seidler also explains same principle for three-dimensional spatial arrangement as highly influenced by Theo van Doesburg's painting Space-time construction #3 (1923)[35] in which there is an interpenetration of space and spatial flow between hovering planes which creates "an openness which is so much more subtle than it is when it's totally open and which is so often done"[36] "Architecture in recent times has been immensely concerned about this idiom of the exploitation of the interior space which involves this simultaneous viewing of things, the channeling of vistas between its elements.

... As Le Corbusier has said, 'Instead of the eye and the mind being abruptly halted by edges and containing surfaces, as had been the case in the past, they are now laid continuously on an exploration, never quite comprehending the mystery of layered and veiled space'."

There is a temptation with the seeing of things that are not entirely apparent, the tantalising sense of the beyond which you in fact are denied and which entices a person to move through and try and explore an interior.

[34] Thus, later in his career, he sought to use more thermally stable materials like reinforced concrete and to respond to the Australian climate by the extensive use of sunshades and flamboyantly-shaped rain protecting canopies on his skyscrapers, (such as Grosvenor Place, Riverside Centre, and QV1), large covered balconies in his houses, as well as shaping his designs to maximize views and enjoyment of the outdoors from inside.

Seidler also arranged in 1966 for the Australia Square tower ground lobby to display tapestries by Le Corbusier and Victor Vasarely – these were replaced in late 2003 by the Sol LeWitt mural.