The public worship of the Roman Catholic church is its liturgy, principally the Eucharist, which is also called the Mass. After the recitation of prayers and readings from the Bible, the presiding priest invites the faithful to receive communion, understood as sharing in the sacramental presence of Christ. At the Sunday liturgy the priest preaches a sermon or homily, applying the day's biblical texts to the present lives of believers.

The church observes a liturgical calendar similar to that of other Christians, following a cycle of Advent, Christmas, Epiphany, Lent, Easter, and Pentecost. It also follows a distinctive cycle of commemoration of the saints.

The worship of the church is expressed as well in rites of baptism, confirmation, weddings, ordinations, penitential rites, burial rites or funerals, and the singing of the Divine Office. A distinguishing mark of Catholic worship is prayer for the dead.

Eucharist ~ In the Presence of the Lord Himself

This is often called the greatest sacrament because Christ himself is present in the consecrated bread and wine. The catechism points out that the Holy Eucharist is both a sacrifice and a sacrament. As a sacrifice the Holy Eucharist is the Mass. The Mass is that divine action in which Jesus, through the agency of the human priest, changes the bread and wine into His own Body and Blood and continues through time the offering which He made to God on Calvary—the offering of Himself for mankind. It is at the consecration of the Mass that the sacrament of the Holy Eucharist comes into being. It is then that Jesus becomes present under the appearance of bread and wine. As long as the appearances of bread and wine remain, Jesus remains present and the sacrament of the Holy Eucharist continues to there exist. The act by which we receive the Holy Eucharist is called Holy Communion. We might say that the Mass is the "making" of the Holy Eucharist and Holy Communion is the receiving of the Holy Eucharist. In between the two, the sacrament of the Holy Eucharist continues to exist (as in the tabernacle) whether we receive it or not.