In 1985, at the Pontifical Faculty of Theology in Wroclaw he defended his thesis, ‘The Relationship of Man and God in the Light of Martin Buber’s Philosophy of Dialogue’, written under the direction of Ignacy Dec (formerly the first bishop of Świdnica).

In 1987, he obtained a master of theology at the Pontifical Faculty of Theology in Wroclaw and was sent to Rome for further studies at Pontifical University of Saint Thomas Aquinas, which he ended in 1991, defending his academic dissertation in Italian ‘Gli Elementi della spiritualità sacerdotale nel pensiero di Hans von Balthasar’ (English: The Components of Priestly Spirituality in the Thought of Hans von Balthasar).

After returning to Poland, he served as spiritual director at the Metropolitan Seminary in Wroclaw and taught at the Pontifical Faculty of Theology, there.

In 1997, he was did habilitation of theology on the basis of his work, ‘Ewangelikalna duchowość nowego narodzenia a tradycja katolicka’ (English: Evangelical Spirituality of the New Birth and Catholic Tradition).

He is the General Vicar of the Archdiocese of Wroclaw, a delegate of the Conference of the Polish Episcopate for the Movement of Nazareth Families and the ‘FIDES’ Federation of Church Libraries.

On 29 June 2021 Pope Francis appointed Siemieniewski as the new bishop of the Diocese of Legnica, replacing the retiring Zbigniew Kiernikowski.