MST is canonically a Society of Apostolic Life of Major‑Archiepiscopal right. The society’s charism is wholly “mission ad gentes” — evangelization and service in regions where the Gospel has limited or no presence, both within India and abroad.

From humble beginnings with around 18–21 diocesan priests pledging full‑time missionary commitment, MST has grown significantly over the decades. Its central administration is located at “Deepti Bhavan, Melampara, Bharananganam, Kerala.”

Today, MST operates through multiple mission regions and delegations. Its mission regions include:
• St Paul Mission Region (Ujjain) — covering Syro‑Malabar dioceses in North India,
• St Thomas Mission Region (Mandya) — covering Karnataka, Tamil Nadu, Andhra Pradesh, Telangana,
• St Alphonsa Mission Region (Sangli) — covering Maharashtra, Goa, Gujarat.
There is also a delegation in Delhi: St Mary Queen of Missions Region.

MST’s apostolate is multifaceted: besides proclaiming the Gospel, its members engage in pastoral ministry, education, health care, social upliftment, work among marginalized and migrant communities, rehabilitation, vocational training, disaster relief, and ecological and social development. Through such service, MST aims to incarnate Christian values of justice, peace, charity, and human dignity.