Eventually, he decided to join the Jesuits, but his father, who wanted Rudamina to become a statesman, was strictly opposed to this idea.

[2] Rudamina abruptly ended his studies at Leuven and returned to Lithuania once he found out that his father was gravely ill.

At that time, he befriended Andrew Bobola, who came to be known as the Apostle of Lithuania and became a saint, as well as Maciej Kazimierz Sarbiewski, a renowned Jesuit poet.

[3] In 1622, Rudamina, together with a small number of other young and talented Jesuits from Vilnius, were sent to Rome to continue with their theological studies at the Roman College.

After receiving the consent of the Superior General of the Society of Jesus, Mutio Vitelleschi, to go on a mission to China on 5 September 1624, he left Rome for Lisbon.

[4] After the missionary preparations in Lisbon, at the beginning of March 1625, along with eleven Portuguese Jesuits, he sailed to Goa, which he reached on 22 August 1625.

[3] At the very beginning of his stay in India, however, Rudamina suffered from malaria and his superiors sent him to Macao where the climate was better for his fragile health.

[5] The superiors concerned about his deteriorating health sent him at the end of 1628 to the Fujian Province, where several hundred Christians lived, in order to help Father Giulio Aleni.

[5] Working together, he and Aleni published an important book in Chinese titled Kouduo Richao 口鐸日抄 (A Diary of Oral Admonitions).

Therefore, he usually did local pastoral work by explaining the teachings of the Catholic faith, visiting and comforting the sick, receiving guests, as well as preaching and hearing confessions.

His catechetical method making use of pictures of the Cor Jesu (Heart of Jesus) was also an effective tool in evangelization.