He came into prominence in 1975 when he took on then prime minister Indira Gandhi for imposing a state of emergency and worked as an underground activist.
But his outspoken character often caused ripples within the government.
Mr Fernandes, aged 70, was first elected to parliament in 1967 and founded his own Samata party in 1994.
He has held several ministerial portfolios including communications, industry, railways and defence and was the only Christian minister in Prime Minister Vajpayee's cabinet.
He came into prominence in 1975 when he took on then prime minister Indira Gandhi for imposing a state of emergency and worked as an underground activist.
He was once detained on charges, later dropped, of smuggling dynamite to blow up government establishments in protest against the state of emergency.
His first term as defence minister of the country was in 1998 when India conducted its shock nuclear tests.
Rift with China
Following the nuclear tests, Mr Fernandes caused a diplomatic rift with China, which he described as India's "enemy number one."
He later denied the statement, saying it was wrongly interpreted.
A year later, the Kargil conflict with Pakistan-backed forces on the disputed Kashmir border again thrust him into the limelight.
Controversy hit Mr Fernandes early in his ministerial tenure when he held a convention of organisations supporting Sri Lanka's Liberation Tigers of Tamil Eelam (LTTE) on the lawns of his official residence.
Aung San Suu Kyi supporter
Mr Fernandes openly supported the LTTE's struggle for a separate state in northern Sri Lanka.
He is also a high-profile supporter of the Burma pro-democracy movement, displaying a wall-size picture of Aung San Suu Kyi in his official bungalow, where Burmese underground leaders are frequent visitors.
As a minister, however, Mr Fernandes was particularly popular among soldiers on the front.
He made 18 visits to the icy heights of the Siachen glacier, "the world's highest battlefield" where Indian and Pakistani troops guard their respective stretches of the glacier through the year.
He was also known for overseeing a huge increase in India's defence budget as compared to the allocations made by previous governments.