Unlike priestly first blessings, diaconal first blessings are not a custom in the Catholic Church. A deacon, however, is never required to deny a blessing to one who freely asks.
Unlike bishops and priests, deacons are ordained “not unto the priesthood, but unto the ministry of service” (Lumen Gentium, 29). The priest’s authority to bless is closely tied to his power to consecrate the Eucharist; the deacon’s authority to bless, however, depends more on the Church’s delegation of that authority. Consequently, the deacon “can impart only those blessings expressly permitted by law” (Code of Canon Law, Can. 1169 §3).
The liturgical books permit the deacon to celebrate many different blessings, for example, those related to baptisms, weddings, funerals, the Liturgy of the Hours, and most of the blessings contained in the Book of Blessings. Appendix II of the Book of Blessings provides a series of solemn blessings and prayers over the people that can be used in conjunction with another liturgical rite or “on any occasion when a priest or deacon is asked to give a blessing.” Thus, the deacon is authorized to respond to virtually any pastoral need.
If the deacon anticipates being approached for blessings, he should consider carrying with him the Shorter Book of Blessings or memorizing at least one of the prayers over the people from the Book of Blessings.
So, for example, if approached by someone seeking a blessing, the deacon could use the following simple formula from the Book of Blessings: “Lord, bless your people and fill them with zeal. Strengthen them by your love to do your will. We ask this through Christ our Lord. R/. Amen. May almighty God bless you, the Father, + and the Son, and the Holy Spirit. R/. Amen.”
Without scruple, the deacon may preface this formula with an extemporaneous prayer.
Responding to a pastoral need, however, is different from initiating an occasion for blessings. The deacon should not, for example, set up a prie-dieu in the receiving line after his ordination to solicit requests for first blessings, a practice appropriately associated with priestly ordination. If someone spontaneously asks the newly ordained deacon for his blessing, though, he may oblige in accordance with the liturgical books.
—Answered by Father Don Anstoetter, Directory of Liturgy, Kenrick-Glennon Seminary, St. Louis, MO