The 17 new advisers named Saturday include priests, laymen and two women.
The experts in liturgy and theology join 27 cardinals and bishops named as full members in October.
That reshuffling removed tradition-minded cardinals Raymond Burke and George Pell from the roster, although other conservatives were kept on.
The office is responsible for ensuring Masses and other sacraments are celebrated around the world according to Vatican standards.
It is headed by Guinea’s conservative Cardinal Robert Sarah.