Więckiewicz graduated from the Faculty of Acting at the Theatre Academy in Wrocław. After graduation, he joined the Polish Theatre in Poznań. He made his debut there in the double role of George Gibbs and Wally Webb in Our Town by Thornton Wilder, directed by Jan Błeszyński (1993). Więckiewicz played on the Poznań stage until 1998.
Later, he appeared in a more contemporary repertoire, in Brutalist plays created by the Theatre Society, which was founded by Paweł Łysak and Paweł Wodziński. He starred in Shopping and Fucking by Mark Ravenhill (1999) and Fire in the Head by Marius von Mayenburg (1999) directed by Łysak, as well as Blasted by Sarah Kane, directed by Wodziński (1999). Więckiewicz worked with Łysak again in 2001 in the Polish Theatre in Poznań where he played Michał in Wolność (editor's translation: Freedom) based on Leon Kruczkowski.
He has also cooperated with theatres in Warsaw. In the years 1999-2001 he worked at the Rozmaitości Theatre, where he played Rogozhin in Prince Myszkin based on The Idiot by Fyodor Dostoyevsky, directed by Grzegorz Jarzyna (2000), and the Actor in Shakespeare’s Hamlet, staged by Krzysztof Warlikowski (2001), among others.
Więckiewicz vividly portrayed Titus in the highly popular Testosteron (Testosterone), a story about seven frustrated men by Andrzej Saramonowicz, directed by Agnieszka Glińska (2002) in the Montownia Theatre in Warsaw. He collaborated with the National Theatre, where he was the King in Marek Modzelewski’s Koronacja (Coronation) directed by Łukasz Kos (2004). The King represents the alter-ego of the main character – a thirty-year-old doctor who tries to rebuild his life after the break-up of his relationships and the death of his father. In Więckiewicz’s performance the King made self-ironic comments on reality and the actions of the protagonist, revealing the truth with no mercy. Then the actor played Konrad Stefaniak in Saramonowicz’s 2 Maja (May 2nd) directed by Glińska (2004), a failed attempt to settle accounts with the Communist past.
Więckiewicz also performed in the Television Theatre. On the small screen he appeared in a contemporary repertoire, playing Stiopa in Janusz Głowacki’s Czwarta Siostra (The Fourth Sister) directed by Agnieszka Glińska (2003) and Daniel in Agnieszka Lipiec-Wróblewska’s Ameryka, część druga (America, Part Two) by Biljana Srbljanović (2006). He took part in two TV shows by Piotr Łazarkiewicz – as Vitaly in the Dead Princess by Nikolai Kolyada (2004), and one of the characters in Fotoplastikon by Krzysztof Bizio (2005).
The actor’s film debut took place in 1993 in A.W.O.L. by Feliks Falk showing the brutal world of military barracks and the so-called ‘wave’ phenomenon (the creation of an informal hierarchy and subculture among soldiers doing compulsory military service). His first major roles were in films by Tomasz Konecki and Andrzej Saramonowicz. He played the wannabe screenwriter Mateusz in the comedy Pół Serio (Half Joking, 2000), which accurately and ironically portrays the Polish film community, and the former organist and gravedigger Julek in Ciało (Body, 2003) – an intelligent pastiche of gangster films filled with absurd humour.
A year later Więckiewicz starred in the crime comedy Vinci by Juliusz Machulski, in the leading role of Robert Cumiński ‘Cuma’, who is ordered to steal the painting Lady with an Ermine after getting out of jail. The actor received an honourable mention for this role at the Noir in Festival in Italy. Due to his tough-guy look Więckiewicz has often been cast as a mafia soldier and other underworld characters. For example, in the series The Officer by Maciej Dejczer (2004-2005) he played Cypa, an ‘axeman’. The actor excelled in such powerful, sensational cinema. The culmination of this type of role was the well-played, multidimensional character of Jan 'Blacha’ Blachowski from a Pruszków gang, a ruthless thug and yet an emotional man capable of sacrifice who begins to cooperate with the police. ‘Blacha’ was first portrayed in the dramatic series Odwróceni (Insiders) directed by Jacek Filipiak, Jarosław Sypniewski, Michał Gazda and Urszula Urbaniak (2007), which later became the basis of the feature film The State Witness (2007).
In 2007, Andrzej Więckiewicz played in All Will Be Well by Tomasz Wiszniewski – a thrilling representation of a small boy’s big trip to Częstochowa to pray for a miracle – curing his mother of cancer. Paweł is a talented athlete, who is accompanied by his P.E. teacher Andrzej – a coach and inveterate alcoholic.