Confesor GO detects a user's location and shows the location of priests around them who are ready to listen to their sins as well as the shortest route to get to him.
It also provides basic information about the priest, including his name, date of birth and the year he was ordained as well as a list of the Ten Commandments.
"The priest may be in a confessional in a church or some place down the street or at a park in your city," reads the description of the app on Apple's iTunes store.
The app will be launched on Thursday on the Feast of the Immaculate Conception, a national holiday in Spain which celebrates the belief that the Virgin Mary was conceived without sin.
A beta version has been downloaded several thousand times since it was made available to the public in late September.
The bishop of the northern city of San Sebastian, Jose Ignacio Munilla, is one of around 100 clerics across Spain who have so far signed up to use the app to signal when they are available to hear confession, which usually involves admitting sins to a priest in a confessional booth.
Father Ricardo Latorre, who came up with the app, said he hopes the service will become available in other Spanish-speaking nations in Latin America next year.
"It has generated a great deal of interest and there are many priests from these countries that ask to join. What happens is things take time and it is impossible to do it faster," he told Catholic news website Verdad en Libertad earlier this year.
While Catholicism remains deeply embedded in Spanish culture, regular church attendance in Spain, like elsewhere in Europe, has steadily fallen.
The majority of Spaniards, 59.3 percent, say they "almost never" attend mass, according to a survey published Monday by the Sociological Research Centre (CIS). Just 15 percent said they went every week.