Thakkar practised on Civil, Criminal, Income-Tax, Industrial Disputes and Company matters before the then Saurashtra High Court at Rajkot and Bombay High Court. He worked in the Gujarat High Court since 1960 to 1963. He was appointed as the Judge in City Civil and Sessions Court on 23 January 1963. Thakkar also served as Special Judge and Additional Judge in the Gujarat High Court. He became the Permanent Judge of the same High Court on 27 November 1973. Thakkar was elevated to the post of Chief Justice, Gujarat High Court on 20 August 1981. He was appointed as a Justice of the Supreme Court of India in March 1983. He was the head of the investigating Thakkar Commission for the Assassination of Indira Gandhi. After his retirement, Justice Thakkar was appointed Chairman of Twelfth Law Commission of India in 1988.