The discussion of Alacoque's own mission and qualities continued for years after her death. All her actions, her revelations, her spiritual maxims, her teachings regarding the devotion to the Sacred Heart were subjected to the most severe and minute examination. Finally the Sacred Congregation of Rites passed a favorable vote on the heroic virtues of this "servant of God." In March 1824, Pope Leo XII pronounced her Venerable and on 18 September 1864 Pope Pius IX declared her Blessed. When her tomb was opened in July 1830, two instantaneous cures were recorded to have taken place. Her incorrupt body rests above the side altar in the Chapel of the Apparitions, located at the Visitation Monastery in Paray-le-Monial, and many striking blessings have been claimed by pilgrims attracted there from all parts of the world. Alacoque was canonized by Pope Benedict XV in 1920 and her feast day is October 16.
In his 1928 encyclical Miserentissimus Redemptor, Pope Pius XI affirmed the Church's position regarding the credibility of her visions of Jesus Christ by speaking of Jesus as having "manifested Himself" to Saint Margaret Mary and having "promised her that all those who rendered this honor to His Heart would be endowed with an abundance of heavenly graces".
Alacoque's short devotional writing, La Devotion au Sacré-Coeur de Jesus (Devotion to the Sacred Heart of Jesus), was published posthumously by J. Croiset in 1698, and has been popular among Catholics.