While in Odessa, Sleževičius became politically involved, with Juozas Gabrys taking credit for converting him to the Lithuanian nationalist cause. He was also involved in a number of cultural and religious activities, organizing courses, concerts and plays, and arranging for religious mass in Lithuanian language. Sleževičius took part in the Russian Revolution of 1905, maintaining public order together with other volunteers. That same year, he represented Odessa Lithuanians in the Great Seimas of Vilnius and started contributing to the newspaper "Lietuvos ūkininkas".