Rev. Fr. Daniel Mathai, affectionately known as Dennis Achen, was born and raised on Long Island, New York. He earned a Bachelor of Science in Business Management from Manhattan College before enrolling in the
Master of Divinity program at Saint Tikhon's Orthodox Theological Seminary Seminary in South Canaan, Pennsylvania, graduating in 2008. He subsequently completed the Postgraduate Program in Liturgical Order and Praxis at the Orthodox Theological Seminary in Kottayam, Kerala, India, and later earned a Master of Business Administration from Saint Leo University.

Before entering full-time parish ministry, Fr. Daniel served for over a decade as a clinical chaplain with the United States Department of Veterans Affairs, ministering at VA Medical Centers in Houston, Minneapolis, and Tampa. As a staff chaplain, he provided pastoral and spiritual care to patients in acute care, hospice and palliative care, mental health, rehabilitation, and addiction recovery settings.

Fr. Daniel was ordained to the Subdiaconate His Eminence Metropolitan Mathews Mar Barnabas, and was subsequently ordained to the Holy Diaconate and Holy Priesthood by His Eminence Metropolitan Zachariah Mar Nicholovos.

Since 2020, Fr. Daniel has been serving as the Vicar of St. Andrew Malankara Orthodox Church in Glenwood Landing, New York, a parish of the Northeast American Diocese. In addition to his parish responsibilities, he serves as Vice President of the MGOCSM of the  Northeast American Diocese and as Executive Assistant to the Diocesan Metropolitan, His Eminence Zachariah Mar Nicholovos.