He did a course in social work in the University of Chicago, U.S.A. Jacob joined Bharat Sevak Samaj in 1954, which is a non-political voluntary organisation, with Prime Minister Jawaharlal Nehru as its president and Gulzarilal Nanda, Union Minister, as Chairman, commenced work to enlist public cooperation for India's planned development.

He also worked as Zonal Organiser for South India for "labour and social service camps for student and youth" - a scheme under the Union Ministry of Education.

Later he took the assignment as Chairman, Bharat Sevak Samaj, Kerala State and Vice-Chairman, Central B.S.S.

He also served as Director of Indian Overseas Bank (1977–82) Kerala State Red Cross etc.

He is an elected member of AICC for many years.He worked in as General Secretary and Treasurer of Kerala Pradesh Congress Committee, Chairman, Kerala State Sevadal He published 'Bharat Sevak' a social worker's journal and was the Chief editor of 'Congress Review', fortnightly published from Trivandrum and the Managing Director of Veekshanam - a Malayalam daily newspaper published from Cochin.

He was also delegate to International Seminar on 'Social Administration' in Western Reserve University, Cleveland, Ohio, USA (1976) and member of Indian delegation to Malaysia (Kuala Lumpur) for the International conference of natural Rubber Producing Countries (1975).

He was the leader of the Indian Delegation to Sri Lanka for the 'International Conference of Natural Rubber Producing Countries' (1980).

As Deputy Chairman Rajya Sabha, Jacob attended the Commonwealth Parliament conference in London in 1986.

He attended the United Nations General Assembly, New York (1985 and again in 1993) and the Human Rights Conference held at the European Parliament in Strasbourg, France (1993).

Jacob had a keen interest in the traditional forms of local democracy in tribal areas, particularly in Meghalaya, and advocated a marriage of modernity and tradition to strengthen grassroots democracy in tribal areas.