After graduating from high school, Mónika Szelei enrolled in the Education and Training Centre for Foreign Trade's international trade and sales programme before completing the textile design and model-drawing assistant course of the Rothschild Klári High School of Apparel Design. Afterwards, she started working in the theatre world as a costume fabricator and worked on productions – including on works for the stage, short films and videos – both in Budapest and elsewhere in Hungary. In 2007, she joined the Hungarian State Opera's men's costume shop as an intern working under Attila Benedek, and by 2010 was employed as one of the Opera's regular costume fabricators. Between 2010 and 2016, as a costume fabricator, assistant costume designer, and costume designer, she took part in realising and staging countless operas, ballet and other productions at the Opera. She made her début as a costume designer in Nina Dudek's 2015 production of Fedora, which was followed by Péter Novák's production of West Side Story. In that same year, she started her studies in set design at the Dresden Academy of Fine Arts, which she later continued at the Hungarian University of Fine Arts under the guidance of Edit Zeke, Piroska E. Kiss, György Csík and Judit Csanádi. Since 2016, she has worked as a freelance designer on productions both in Hungary and abroad. Her most recent production at the Opera was Miklós Szinetár's production of Bluebeard's Castle in the spring of 2018. During the 2018/19 season, she will be working on Tibor Bogányi's Carmina Burana and Ádám Tulassay's Edgar.