Reema Sen was born in Kolkata on 29 October 1981. She completed high school from St. Thomas Girls School in Kidderpore, Kolkata, after which her family moved to Mumbai.

In April 2006, a Madurai court issued non-bailable warrants against Sen and Shilpa Shetty for "posing in an obscene manner" in photographs published by the Tamil newspaper Dinakaran, owned by Sun Group. The report stated that the two actresses had failed to comply with earlier summons for the same reason, hence the issuance of the warrants. The petitioner submitted that the paper had published "very sexy blow-ups and medium blow-ups" in its December 2005 and January 2006 issues, and which allegedly violated the Indecent Representation of Women (Prohibition) Act 1986, Young Persons (Harmful Publications) Act 1956, and the Indian Penal Code Section 292 (Sale of Obscene Books). The petitioner further demanded that the images should be confiscated under the terms of the Press and Registration of Book Act 1867.

In January 2007, outgoing Chief Justice Y. K. Sabharwal confirmed that Sen had written to him in order to enunciate guidelines against frivolous lawsuits against artists, but declined her plea on the grounds that she should have filed a formal petition instead of writing a letter.

Reema Sen married businessman Shiv Karan Singh in 2012. She gave birth to their first child, son Rudraveer, on 22 February 2013.