The word “Mass“, when referring to the Most Holy Sacrifice of the Mass, should always be capitalized. ... Catholic Mass, as written with the upper-case initial, also functions to identify itself as a proper noun describing the specific liturgical ritual where the Eucharist is celebrated.

Do you capitalize Mass as in Catholic Mass?

Always capitalize when referring to the ceremony, but lowercase any preceding adjectives: high Mass, low Mass, requiem Mass.

Is Mass capitalized AP style?

AP Style tip: Mass is celebrated, not said. Capitalize when referring to the ceremony; lowercase preceding adjectives: requiem Mass.