The parish of Mellieha, dedicated to the nativity of Our Lady, originally consisted of a complex of two adjoining caves which developed into the first parish church. It is the earliest such church (troglodytic church) which is still in use today. In the 1700s, to better serve the larger number of parishioners, this parish church was enlarged by breaking down one side of the main cave and adding a larger building to it. In the late 1800s this was in turn replaced by a much larger parish church. Meanwhile, the troglodytic church of Our Lady of Mellieha continued to hold its role as a place of pilgrimages.

At present, the parish is administered by Fr Joe Caruana, the parish priest, while Fr Mario Dimech is the assistant parish priest. Together with Fr Moses Debono, Fr Joe Farrugia and Fr Joe Mifsud, they form the clergy of this parish.

The parish includes two religious houses, one run by the Sisters, Daughters of the Sacred Heart and a retreat house, La Salle Retreat House, run by the De La Salle Brothers.

The parish also includes a number of groups which help in the church administration, as well as the formation and the support of parish members. These groups are made up of lay people who work on a volontary basis. The number of these run in the hundreds.