While in the convent, Jeanine Deckers wrote, sang and performed her own songs, which were so well received by her fellow nuns and visitors that her religious superiors encouraged her to record an album, which visitors and retreatants at the convent would be able to purchase. In 1961, the album was recorded in Brussels at Philips; the single “Dominique” became an international hit, and in 1962 her album sold nearly two million copies. The Dominican Sister became an international celebrity, with the stage name of Sœur Sourire (“Sister Smile”). She gave concerts and appeared on The Ed Sullivan Show on 5 January 1964. “Dominique” was the first, and remains the only, Belgian song to be a number one hit single in the United States. Deckers found it difficult having to live up to her publicity as “a true girl scout”, always happy and in a good mood. “I was never allowed to be depressed”, Deckers remembered in 1979. “The mother superior used to censor my songs and take out any verses I wrote when I was feeling sad.” In 1963 she was sent by her order to take theology courses at the University of Louvain. She liked the student life, if not her courses. She reconnected with a friend from her youth, Annie Pécher, with whom she slowly developed a very close relationship.

In 1965, Debbie Reynolds starred in The Singing Nun, a biographical film loosely based on Deckers. Jeanine Deckers reportedly rejected the film as “fiction”. Deckers did not gain much from this international fame, and her second album, Her Joys, Her Songs, did not receive much attention and disappeared almost as soon as it was released. Most of her earnings were in fact taken away by Philips and her producer, while the rest automatically went to her religious congregation, which made at least $100,000 in royalties. Pulled between two worlds and increasingly in disagreement with the Catholic Church, she left the convent in 1966, to pursue a life as a lay Dominican of the order. She later reported that her departure resulted from a personality clash with her superiors, that she had been forced out of the convent and did not leave of her own free will. She still considered herself a nun, praying several times daily, and maintaining a simple and chaste lifestyle. After she left the convent, her recording company required her to give up her initial professional names of “Sœur Sourire” and “The Singing Nun”. She attempted to continue her musical career under the name “Luc Dominique” and pursued social work. Increasingly frustrated at what she perceived to be the Catholic’s Church failure to fully implement the reforms of the Second Vatican Council she released a song in 1967 defending the use of contraception called “Glory be to God for the Golden Pill” This led to an intervention by the Catholic hierarchy in Montreal, Canada, which resulted in one of her concerts being cancelled. Jeanine Deckers released an album entitled I Am Not a Star in Heaven. Her repertoire consisted of religious songs and songs for children. Despite her renewed musical emphasis, Deckers’ career failed to prosper. She blamed lack of success of the album on not being able to use the names by which she had become known, saying that “nobody knew who it was”. She suffered a nervous breakdown followed by two years of psychotherapy.

In 1973, Deckers became involved with the Catholic Charismatic Renewal. Cardinal Suenens requested that she write songs for the movement, and this led to a brief but successful return to the stage, including a visit to Pittsburgh, where she sang before several thousand people. Under the name “Sister Smile”, she released another album in 1979, which she described as containing “honest, religious songs” and commented that the album would help listeners to “know who I really am.” In the late 1970s, the Belgian government claimed that she owed $63,000 in back taxes. Jeanine Deckers countered that the royalties from her recording were given to the convent and therefore she was not liable for payment of any personal income taxes. As her former congregation denied responsibility for the debt, claiming both that they no longer had any responsibility for her and that they did not have the funds, Deckers ran into heavy financial problems. In 1982, she tried, once again as Sœur Sourire, to score a hit with a disco synthesizer version of “Dominique”, but this last attempt to resume her singing career failed. In addition to the other financial worries, an autism centre for children started by Annie Pécher had to close its doors for financial reasons in 1982. After this Deckers tried to make a living by giving lessons in music and religion.

Citing their financial difficulties in a note, she and Annie Pécher died by suicide by taking an overdose of barbiturates and alcohol on 29 March 1985. In their suicide note, Jeanine Decker and Pécher stated they had not given up their faith and wished to be buried together after a church funeral. They were buried together on 4 April 1985 in Cheremont Cemetery in Wavre, Walloon Brabant, the town where they died. The inscription on their tombstone reads “J’ai vu voler son âme/ A travers les nuages” (English: “I saw her soul fly through the clouds”).