She was born in Warsaw on 1st November, 1982. She began systematic singing lessons at the age of 18 at the Józef Elsner State Secondary School in Warsaw under Waleria Przelakowska-Rokita. In 2011, she graduated from Detmold’s Music Academy and earned a degree in vocal studies under Gerhild Romberger and music education. She was awarded a scholarship by the German Academic Exchange Service (DAAD), which enabled her to continue her education at the Royal Swedish Academy of Music in Stockholm under Prof. Petteri Salomaa and Prof. Christina Billing. She also studied musicology at the University of Warsaw. In 2011, she took part in the 'Opera Academy' Young Talents Development Programme at the Grand Theatre –National Opera in Warsaw. In 2012, she graduated from the Interdepartmental Postgraduate Song Interpretation Course at the Fryderyk Chopin University of Music in Warsaw. . In 2015, she completed her PhD studies at the Creative Psychopedagogy Department at the Maria Grzegorzewska Academy of Special Education.
She was awarded many scholarships, mainly by the Richard Wagner Scholarship Foundation, the Werner Richard Foundation – Dr. Carl Dörken and the Hans and Stefan Bernbeck Foundation. In 2009, she became a finalist of the NEUE STIMMEN International Singing Competition. She took part in master classes with such renowned singers and teachers as Olga Pasiecznik, Maciej Pikulski, Jadwiga Rappé, Grace Bumbry, Anita Garanča, András Schiff, Francisco Araíza, Christa Ludwig and Barbara Bonney. She took part in the 47th International Summer Course for New Music in Darmstadt with Donatienne Michel-Dansac. She also attended the Darmstadt Contemporary Opera Workshops. In 2015, she received a scholarship from the Ministry of Culture and National Heritage and qualified for the Ideas Laboratory of the Association for Creative Initiatives ‘ę’ with her original project W[rz]AWA. In 2020, she again received an art scholarship from the Ministry of Culture and National Heritage, this time for the project Critical Guide to Singing in Vocal Music. In 2023, she was awarded a scholarship for artistic research and residency at the Centro Internazionale di Scultura Peccia Lavizzara in Switzerland.
In 2014, Barbara Kinga Majewska debuted in the Grand Theatre – National Opera scene in Sławomir Wojciechowski’s 'Zwycięstwo nad Słońcem' (Victory Over the Sun) [Projekt P]. That same year during the Instalakcje Festival in Warsaw, she performed four world premieres of compositions commissioned for her and the Kwadrofonik ensemble written by Aleksandra Gryka, Andrzej Kwieciński, Wojciech Blenard and Sławomir Wojciechowski. In November 2014, she also took part in the premiere composition performance of Joanna Woźny’s 'Szczęśliwe dni' (Happy Days) along with the pianist Emilia Sitarz and the Kwartludium ensemble. The premiere opened at TR Warszawa as part of the '4 for Beckett' project curated by Paweł Krzaczkowski. In the press material for the Instalakcje Festival for the internet magazine Dwutygodnik.com, Adam Suprynowicz stated:
Barbara Kinga Majewska shows a wide variety of vocal skills, moving smoothly between conventions and the so-called extended vocal techniques. This distinction seems increasingly inappropriate when applied to the context of the Instalakcje Festival. The artist uses the whole wealth of the spectrum of the human voice, utilizing it in such a way that she becomes not a solo artist, but a member of the group. The concert as a performance is a meeting of sorts, of pop culture habits and musical performance studies – music did not suffer here at all (which is not that obvious), but rather naturally added the visual form to the overall presentation of the 4 new compositions.
In June 2015, Majewska created the role of Kławdia Chauchat in Paweł Mykietyn’s opera The Magic Mountain, directed by Andrzej Chyra, with a libretto by Małgorzata Sikorska-Miszczuk. In 2016, at the New Horizons International Film Festival, the artist played Renee and Alice in Olga Neuwirth’s opera Lost Highway, directed by Natalia Korczakowska. The same year, during the Sacrum Profanum Festival, together with the Arditti Quartet, she performed John Zorn’s Pandora’s Box for the first time in Poland.