His actions in official capacity were controversial multiple times including when he undertook to regulate internet content.

[8][9][10][11] He left the Indian National Congress in 2022 to file his nomination for the Rajya Sabha independently but backed by Samajwadi Party.

In the 2004 general elections, Sibal became an MP by winning the Chandni Chowk constituency against TV actor Smriti Irani of the Bharatiya Janata Party (BJP) in the National Capital Territory representing the Congress Party and was inducted into the Cabinet under Prime Minister Manmohan Singh as Union Minister for Science, Technology and Earth Sciences.

He won the constituency of Chandni Chowk for the second time for the Indian National Congress in the Lok Sabha elections of 2009.

[25] Kapil Sibal was indicted by CAG for favoring M/S Phoenix Rose LLC by overlooking rules and regulations and handpicking that company for creating a database for over 500,000 working professionals of People of Indian Origin settled in the US.

CAG's report said that the project's cost was $120,000 but three years after the initiation, the company has dumped the networking site, completing just over 16% of the targeted work.

[26] Also during his time in that office, his move to regulate internet content[27] was criticized across many social networking sites like Facebook, Twitter and Google+.

He led the Indian delegation to the Annapolis Conference, USA, held to gather International support for establishment of a Palestinian state and the realization of Israeli–Palestinian peace during November 2007.

He led the Indian delegation to the United Nations Framework Convention on Climate Change (UNFCCC) at Bali in December 2007.

Satish Jha, chairman of OLPC India, the leading competitor to this venture, questioned his claim that a $35 laptop could be created in a year.

[34][35] This also lead to an open letter by Nicholas Negroponte offering him complete access to MIT and OLPC technologies to help realise India's dream to create a laptop of its own.

[39] An anthology of Kapil Sibal's poems titled I Witness: Partial Observation was published by Roli Books, New Delhi,[40] in August 2008.

Kapil Sibal wrote the lyrics of the songs "Tere bina" and "Mast hawa" for 2016 Hindi film Shorgul.

Sibal was named a "Living Legend of the Law" by the International Bar Association and in 2006, the Government of India honoured him with the 'Padma Bhushan' award for his distinguished services in the field of Public Affairs.