Loveleen Tandan first worked with Deepa Mehta on Earth (1998), and later worked with Mira Nair on three films: Monsoon Wedding (2001), Vanity Fair (2004) and The Namesake (2006). She was also the casting Director (alongside Shaheen Baig) for Brick Lane (2007), directed by Sarah Gavron and adapted from Monica Ali's novel of the same name.

Tandan's most major credit is Slumdog Millionaire (2008), where she initially began as one of the film's casting Directors (with Gail Stevens co-ordinating casting from London) but was, during production on the film, designated as the "Co-Director: India" by Danny Boyle in recognition of her significant contributions in the making of the film. Boyle explained his reasoning behind the credit by stating it was "because I had her there every day, and I kind of relied on her enormously to make sure I didn't make any big mistakes, and obviously, translation for the kids. And translation of the text because obviously, if you translate a line of Simon's literally into Hindi, a seven-year-old is just going to go… So, they had to be given a line that was the equivalent in Hindi." Tandan herself has stated that she was given the co-director credit after she "suggested to Danny and Simon Beaufoy, the Writer of Slumdog, that it was important to do some of it in Hindi to bring the film alive (20% of the film is in Hindi). They asked me to come up with Hindi dialogues which I, of course, instantly agreed to do. And as we drew closer to the shoot date, Danny asked me to step in as the co-director."