The 14-year-old movie star grinned with delight as she recalled her encounter with the former N Sync singer.
'I saw him and went up to him and he was like 'Oh my god you were amazing, are you so excited?'' she told US chat show host Jimmy Fallon.
'I was like 'Well, I'm actually more excited that you're here, but the movie was great'.'
Steinfeld plays Mattie Ross in True Grit, the Coen brothers' 2010 adaptation of the 1969 Western film.
The teenager, who stars alongside Jeff Bridges, Matt Damon and Josh Brolin, told Fallon how her family screamed with excitement when she landed the role.
'I was in my room waiting for a call, not even knowing if I was going to get one or not,' she said.
'The phone rang and I heard my mom pick up the phone. I wanted to listen because I wanted to know what was happening, but I was scared to.
'Finally my mom called me down and she said 'Mattie Ross there's someone on the phone for you'.
'I ran downstairs and my dad was taking pictures of me and everyone was screaming.'