He resumed his professional activity after the war, rebuilding la Pinacoteca di Brera, the Villa Fossati, and the Casa degli Atellani in Corso Magenta, the home of Ettore Conti.

Conti introduced Portaluppi to Milan's high society and he started to have the city's most important families as clients such as Borletti, Fossati, Venti and Crespi, Angelo Campiglio, and Mino Brughera.

Portaluppi "had fallen into relative obscurity, tainted after the war by his professional association with the [Fascist] regime", until 2009 when the Villa Necchi Campiglio was used as a principal shooting location for Luca Guadagnino's film I Am Love.

Starting in 1950 Piero Portaluppi collaborated with Gualtiero Galmanini until his death, establishing himself as a key figure in Italian rationalism.

Although he participated in Galmanini's projects, he did not always sign official documents, and many materials were lost in a fire at the land registry in Milan.