In her early career, at Ateliers Jean Nouvel, Mia Hägg was employed as Assistant Project Manager on the Dentsu Tower, Tokyo and later at, Herzog & de Meuron, as Project Manager for the National Stadium of the 2008 Beijing Olympics. She has been teaching Master and Bachelor levels at UCLovain in Tournai, Belgium and at the Accdemia di Architettura in Mendriso, Switzerland. She is regularly invited to give lectures at academic institutions and to join juries internationally, most recently the 2022 EU/Mies van der Rohe Prize jury.

She participated in the Venice Biennale in 2012 and 2016. Mia Hägg is committee member of Europan Sweden and as of recent of the Swiss Federation of Architects in Ticino.