Since graduating from the École Nationale de théâtre in 1994, Guillermina Kerwin has performed in about forty theatrical productions, notably in such projects as Si la tendance se maintient by François Archambault (1995), Le monde selon Dieu by Claude Legault and Pierre Yves Bernard (1996) and the ensemble La Fête des morts by Céline Bonnier and Nathalie Claude (2002, Momentum).

Guillermina has also worked with Yves Desgagnés in Un Simple Soldat (1998, Jean Duceppe), with Denis Marleau in Dors, mon petit enfant, Comédie and Les Aveugles (2001), with Serge Denoncourt in À la recherche d'Elvis (2003), as well as with Normand Chouinard in L'Hôtel du libre échange at the Théâtre du Nouveau Monde (2004). She also performed in the Ligue Nationale d'Improvisation with André Melançon and Jacques l'Heureux (1995-2002).

Having worked regularly with Robert Gravel and Jean-Pierre Ronfard at the Nouveau Théâtre Expérimental, Guillermina finally signed her own play and directed Amour, Cul, et Violence with Didier Lucien (2007).

More recently, Guillermina played « La-ma-tante-cool-de-Repentigny » in Chante avec Moi (2010), a play by Olivier Choinière. She also personified the role of la Duchesse du Carnaval in the Cabaret Insupportable (Trans-Théâtre 2010). In summer theatre, she performed in the play Jeux Doubles at the Théâtre du Bic.

On television, she plays the role of Eva Molina in the popular children's series Tactik airing on Télé-Québec. On WEB TV she plays Annie St-Gelais in the series www.jackjobin.tv alongside Pierre Lebeau and François Bernier, directed by Marie-Hélène Copti. She is also a cast member of 3600 secondes d'extase with Marc Labrèche.

Guillermina interjects her passion for dance along with her acting talents. In 2011 she performed in the show Un peu de tendresse bordel de merde! by Dave St-Pierre at the Théâtre de la Ville in Paris, France and at Sadler's Well in London, England.