After his graduation, in 1967, he asked for acceptance to the Polish Province of the Society of the Divine Savior. He entered the Novitiate in Bagno on August 5th 1967 and received his religious habit. He took his first religious vows in Bagno on August 15th 1968 and in the same year he began to study Philosophy and Theology at the Salvatorian Major Seminary in Bagno. He served his community as an organist and animator of musical and liturgical life. On August 15th 1973 he made his perpetual profession. He was ordained to the Deaconate on October 11th 1973 in Bagno by the Most Rev. Wincenty Urban. He was ordained to the Priesthood on May 23rd 1974 in Trzebinia by the Most Rev. Stanisław Smoleński.

After the ordination to the Priesthood he was sent to his first place of ministry: The Sacred Heart of Jesus Parish in Oborniki Śląskie, as a parochial vicar. He also taught music and chant at the Salvatorian Seminary in Bagno. He was still considering possibility of continuing his musical education. For that reason he was sent to the religious community house in Kraków at Łobzowska Street, where he engaged in pastoral ministry and worked at the Vocation Center until the beginning of the academic year in Lublin, where then he lived and studied since 1975 until 1980.

After completing the studies he was sent to the Salvatorian Seminary in Bagno, where his duties included teaching music and church singing as well as pastoral ministry usual for the Seminary educators. In order to develop his competence, on January 18th 1981 he asked his superiors for possibility of continuation of the doctoral studies at the Catholic University of Lublin. He was appointed as Director of Studies at the Salvatorian Major Seminary in Bagno and two years later he was sent to the community house in Oborniki Śląskie, as superior and parochial vicar. In 1985 he was released from his duties as a vicar of the Sacred Heart of Jesus Parish in Oborniki Śląskie.  In 1987 he was transferred to the Salvatorian community of Trzebnica as its superior. There he applied his musical talents as organist and conductor of the church choir.

He concluded his doctoral studies on December 4th 1987 at the Catholic University of Lublin. In 1990 he was released from the office of superior and he was entrusted with duties of a consultor and treasurer of the community of Trzebnica. One year later he was released from these duties and was appointed as pastoral assistant at the Parish of Saint Jadwiga in Trzebnica. In 2003 was published a collection of hymns and songs dedicated to St. Jadwiga of Silesia, in three languages: Polish, German and Czech.

In 2006 Fr. Jerzy Sienkiewicz was released from his function as pastoral assistant and stayed in the community as a resident. In 2011 he was transferred to the religious community house in Zakopane as a penitentiary.

Fr. Jerzy Sienkiewicz passed away on September 26th 2013 at the religious community house in Zakopane. He went to Our Lord at the age of 64, in his 39th year as a Priest and after 45 years of religious life.  His funeral took place on September 30th 2013 at the Basilica of Trzebnica. He was buried at the religious community tomb at the local cemetery.