In 1990, Pei retired from full-time practice, however, he still takes on some work as an architectural consultant often for the firm founded by his sons Chien Chung Pei and Li Chung Pei.
Tuttavia, continua a lavorare come consulente architettonico, spesso per Pei Partnership Architects, l’azienda fondata dai suoi figli Chien Chung Pei e Li Chung Pei.