According to the norms of canon law, the Tribunal of the Diocese of Phoenix is the court established by the diocesan bishop in order to adjudicate cases concerning the status of persons, the violation of rights, and the imposition of penalties. The Code of Canon Law and the jurisprudence of the tribunals of the universal Church regulate the legal practice of the Tribunal. Those who have studied the law of the Church, known as canon lawyers, also provide canonical advice to the diocesan bishop, members of the diocesan curia, clerics, and the faithful of the diocese.

Although the diocesan bishop is the chief judge of the diocese, it is not possible for him to personally adjudicate each case. Under the direction of the judicial vicar (a priest appointed by the bishop to preside over judicial matters), a staff of priests, deacons, and laypeople who have been trained especially for such work carries out the ministry of the Tribunal.

A majority of the caseload involves parties who have petitioned for an examination of marriages for a possible declaration of nullity. The Tribunal of the Diocese of Phoenix is also the Appellate Tribunal for the Diocese of Gallup, Tucson, and Santa Fe. There are other various judicial and canonical matters assigned to the Tribunal, including penal cases.