Nació en Milán en dónde cursó sus estudios de arquitectura hasta 1944. Tras finalizar la carrera comenzó a trabajar en el estudio de Livio y Pier Giacomo.

Fue profesor en la Politécnica de Turín y la Politécnica de Arquitectura y Diseño Industrial de Milán, en dónde dirigió la tesis de la diseñadora asturiana Patricia Urquiola.

Una de sus creaciones más usadas es el pequeño interruptor plano típico de la lámpara de la mesita de noche.

Castiglioni studied architecture at the Politecnico di Milano, and graduated in 1937.^[1] In that year^[1] or in 1938^[2] he started an architectural design practice with his brother Livio and Luigi Caccia Dominioni.^[2] He married Maria Coduri de Cartosio on 30 December 1942.^[1]

After the Second World War he and Livio worked with their younger brother Achille, who had graduated in architecture in 1944.^[2] Much of their work was in exhibition design, but they also carried out a number of architectural projects, including the reconstruction in 1952–53 of the Palazzo della Permanente (it), which had been destroyed by bombing in 1943.^[1]

Livio Castiglioni left the practice in 1952^[2] or 1953^[1]. From then until Pier Giacomo died – in Milan, on 27 November 1968 – he and Achille worked as a team; their designs are not attributable to either one of them.^[1][2]

Castiglioni taught life drawing at the Politecnico di Milano from 1964 to 1968.^[1]