In 1963 he returned to India, as a part of the scientist pool scheme initiated by Prime Minister Jawaharlal Nehru to bring back talented Indians working abroad.

He was instrumental in introducing a number of new products under such as speed control for AC and DC motors, static inverters and converters, calculators, electronic clocks, and display systems.

Kerala State Electronics Development Corporation Limited (Keltron) was formed with Nambiar as its first chairman and managing director.

[4][5] In 1985, Indira Gandhi appointed Nambiar as the chairman and managing director of Indian Telephone Industries Limited, the largest public sector company in telecommunications.

In 1986, Nambiar was appointed secretary of the Department of Electronics of Government of India (now the Ministry of Information Technology) by Prime Minister Rajiv Gandhi.

During this stint the Centre for Development of Advanced Computing was formed with Pune as its headquarters merging his earlier initiatives such as ER&DC, Trivandrum to it.

[7] In February 1995, Nambiar under the aegis of KPP Nambiar Associates and its Mauritius based subsidiary Kortech Corporation (with a 24% stake) launched an INR 1471 Crore Naphtha based power project to generate 513 megawatts of electricity under the name of Kannur Power Projects in his native Panchayat of Kalliasseri in the Kannur District in Kerala.

While living in Bombay, he met and married Saroja Kamakshi, mother of Indian classical dancer, Malavika Sarukkai.

He played a major role in developing the Indian electronics industry including the establishment of C-DAC, STPI, CEDTI and VLSI laboratories.

As the founder chairman of Keltron, Nambiar was instrumental in taking electronics to the villages by setting up 50 women's co-operatives that produced most of the company's consumer products.

The concept of women's co-operatives in villages was emulated by various state governments like Punjab, Bihar, Manipur, Pondicheery and Uttar Pradesh.

Keltron also trained unskilled workers into skilled electronic equipment assembly operators, enabling them to work in women's co-operatives in Ranchi, Pondicherry, Imphal, and Lakshadeep.