Grover was born on 23 February 1982 in New Delhi, India to a Punjabi Sikh family. He has one younger brother. When Grover was young his family moved to Al Khobar, Saudi Arabia. He did his schooling in Dammam, Saudi Arabia, and then pursued a degree in Hotel Management from IHM Mumbai. He then worked as a Marketing Executive in the Sheraton Hotel in Oman.
In 2004, he moved back to Mumbai and then pursued a career in modelling and participated in the Gladrags Manhunt Contest and won the award of the "Most Popular Model". In 2013, Grover was listed in Asia's top 50 Sexiest Men on the Planet list, and again in 2014. In 2013 Grover was described as one of the highest paid Indian television actors.
Grover began his television career with Balaji Telefilms' Kitni Mast Hai Zindagi on MTV India. In 2007 he got the show Dill Mill Gayye, a medical youth drama. The Times of India reported that Grover became an "instant hit" and a "teenage icon". It was reported that Grover would routinely report hours late for work. The producers, Cinevistaas Limited, said that they suffered a loss of Rs 2 crore due to his behaviour, had lodged a complaint against him with the Cine & TV Artistes Association, and were planning to sue him to recover their losses. Grover left the show for a while, but returned after 6 months due to fan demands. The show ended on 29 October 2010.
Whilst shooting for Dill Mill Gayye he also participated in a few reality shows, he hosted a dance reality show called Zara Nachke Dikha, contested and became a finalist in the dance reality show Jhalak Dikhhla Jaa (season 3) and also participated in Fear Factor: Khatron Ke Khiladi. Grover was also seen in advertisements of Rupa Frontline, Cleartrip.com, Indian Gem & Jewellery and Kajaria tiles. Later he hosted a Channel V India show called Perfect Couple. He also acted in two shows of Cinevistaas Limited; he featured in Teri Meri Love Stories, and did a cameo in Dil Dosti Dance.
On 29 October 2012, Grover returned to daily fiction with 4 Lions Films' Qubool Hai. The show was given a good time slot and gained popularity pretty early becoming the number 2 show of Indian Television. Grover won two Best Actor Popular Awards for his portrayal of Asad Ahmed Khan. Grover's work at Qubool Hai ended at the end of 2013. The channel, Zee TV, said that it had fired him because of his unprofessional behaviour. He denied the allegations, saying that the channel was trying to defame him, and stated variously that he left because his contract ended or due to ill health.
In 2015, Grover's films Alone and Hate Story 3 were released. International Business Times reviewed Hate Story 3 and wrote "Audiences say Karan Sigh Grover steals the show" He signed the film 3 Dev, a satirical comedy in which he would play the character of Vishnu. Grover hosted a new talk show on ABP News called "Selfie" in which he narrated the story of Bollywood Stars and their struggles. He became the brand ambassador of designer Rocky S's signature Brand RS along with Bipasha Basu. He is also the brand ambassador for UM Motorcycles.
Grover married actress Shraddha Nigam on 2 December 2008. The marriage ended in divorce after 10 months. Grover married Jennifer Winget, his costar from Dill Mill Gayye, on 9 April 2012. In November 2014 Winget stated that she and Grover had separated. Grover also stated through Twitter about his impending divorce from Winget. Grover has stated that he is not religious. Grover is a fitness enthusiast. In 2015, Grover dated Alone co-star Bipasha Basu and got married with her on 30 April 2016.