Recent studies have emphasized the centrality of late medieval mysticism to Martin Luther’s theology of faith. Building upon such research, I argue that Luther’s Freedom of a Christian (1520) preserves a characteristic tension within medieval mysticism: the cohabitation of human agency alongside divine operation. Whereas external agency (good works) is rejected, Luther reintroduces internal human agency within his theology of faith. Contrary to standard views of Lutheran doctrine, Freedom retains some degree of bidirectionality in the relationship between God and the believer. A comparison with Johannes Tauler highlights both Freedom’s indebtedness to medieval mysticism and its radical simplification of the mystical framework.