Maria Kousouni holds a diploma in dance and dance instruction in the Vaganova method from the Despoina Grigoriadou Professional Dance School, where she was taught by Galina Bogoeva, Boriana Rizova, Milena Simeonova and Evridiki Gregoriou.

She began her career in 1999 when she was offered a place with the Vienna State Opera Ballet. She was with the company for five years (1999-2004) and performed a number of roles in major dramatic repertory ballets, including: Romeo and Juliet (Cranko/Prokofiev), Spartacus, Medea, Firebird, Rite of Spring and Bolero (Renato Zanella), La Bayadère (Natalia Makarova), Zorba (Lorca Massine), Giselle (Chernikova), Petite Mort choreographed by Jiři Kylian, Slingerland (William Forsythe), Polyphonia (Wheeldon), Pas de deux and Theme and variations (Balanchine/Tchaikovsky), The Nutcracker (Strømgren/Tchaikovsky), Adagio Hammerklavier (van Manen) and others. She has danced in the Vienna Philharmonic New Year's Concert three times.

She has also worked with the John Neumeier Hamburg Ballet and the Hamburg State Opera where, under the guidance of John Neumeier himself, she danced in the ballets Requiem, Nijinski, Preludes CV, As You Like It and Death in Venice, The Nutcracker, The Wayward Daughter (Ashton), Sleeping Beauty, Mahler, Mahler IIV and others. In 2001, she won a Special Prize at the International Dance Competition of Luxembourg.

In 2007 she joined the Greek National Opera Ballet as principal dancer. She has danced leading and/or supporting roles in the ballets Zorba (Massine/Theodorakis), Giselle (Mukhamedov/Adam), Eugene Onegin (Mukhamedov/Tchaikovsky), Le Corsaire (Petipa/Adam), Gioconda’s Smile (Zanella/Hatzidakis), Journey to Eternity (Zanella/Karaindrou), Snow Queen (Barra/Glazunov), Romeo and Juliet (Zanella/Prokofiev) and others. Maria also choreographed the production of the operetta Die Fledermaus (2013-14).

She teachers at the Greek National Opera Professional Dance School.