The paper explores the influence of the Helsinki Accords on Catholic institutions and networks in the Soviet Union during the final decades of the Cold War. The paper would examine how the Vatican's Ostpolitik and the emphasis on religious liberty shaped the activities of underground Catholic communities and their interactions with both Soviet authorities and global Catholic networks. The paper will also address the broader impact of Helsinki's principles on Catholic conceptions of human rights and religious freedom in the Eastern bloc, contributing to the dialogue on how the Church adapted to geopolitical challenges during this period of transformation.