Queralt Casasayas has been teaching voice in the Institut del Teatre Barcelona. As an actress she has has participated in theater productions such as: Galileu, B.Brecht directed by Carme Portaceli (Teatre Capitol); Fairfly, Joan Yago, directed by Israel Solà (Teatre Tantarantana); Hamlet, W.Shakespeare, directed by Raimon Molins i Marc Choret (Teatre Àtrium); Les troianes, J.P.Sartre, directed by Anna Estrada (Teatre Akadèmia); Fedra, J.Racine directed by Sergi Belbel (Teatre Romea); Les supertietes, Anna M Ricart, directed by Mònica Bofill (Círcol Maldà); Nit de reis, W.Shakespeare, directed by Adrià Aubert (Círcol Maldà); Fuenteovejuna o breve tratado sobre las ovejas domésticas, Anna M Ricart, directed by Ricard Soler; El Cantador, Serafí Pitarra directed by Xicu Masó (Teatre Nacional de Catalunya); Sota el llit, Núria Bizcarro, directed by Ricard Soler (Teatre Nacional de Catalunya); La filla del senyor Bianchi, Gianni Rodari directed by Cia Les Bianchis (Teatre Akadèmia); La Bête, David Hirson, directed by Sergi Belbel (Teatre Nacional de Catalunya); Llàstima que sigui una puta, John Ford directed by Anna Estrada (Teatre Akadèmia); Fora de joc, Sergi Belbel, directed by Cristina Clemente, (Teatre Capitol); La corda fluixa (Círcol Maldà); Espectres, H. Ibsen directed by Magda Puyo (Teatre Romea); L'agressor directed by Carme Portaceli.
