Auxiliary membership is open to Priests, Religious and lay people who wish to associate themselves with the Legion by undertaking a service of prayer in its name. It provides individuals, who are unable to assume the full duties of active membership, an opportunity to support the Legion and its active members.

Auxiliary members commit to daily recitation of the prayers comprised in the Tessera, namely: the invocation and prayer of the Holy Spirit; five decades of the Rosary and the invocations which follow them; the Catena; and the prayers described as "concluding prayers". These prayers may be divided throughout the day, as convenient.

Individuals who are already saying a daily Rosary for any intention whatsoever may become auxiliary members without an obligation to say an additional Rosary.

Auxiliary members, although unable to commit to the requirements of active membership, are welcome to participate in other Legion activities when possible.