Spears is centre of attention with the cast
The 20-year-old singer attended the event with her long-term boyfriend, N'Sync member Justin Timberlake.
In the film, she plays an American teenager who embarks on a voyage of discovery with two childhood friends, in search of her mother,
Spears said she was not fearful of a flop and repeating the ignominy endured by singer Mariah Carey over her film Glitter.
The film, starring Carey, earned worst film and worst actress nominations at the Razzies awards.
'Curious'
Spears said: "It wasn't easy for me. The whole transition was a little scary at first, but I'm so happy I did it.
The film is geared very much for teenage audiences and centres on many teen issues.
Spears said she was not sure the film would be suitable for some of her younger fans.
"I think that it's up to the parent to decide. My sister's 10 years old and she went to go see the movie and she loved it," she said.
On the subject of her future film career, Spears said she was ambitious and was keen to challenge herself.
"I like to push myself and so it made me want to really go there just to see if I could do it. Just to see.
"But it's not even so much about it being the biggest movie in the world, as long as my fans can go to it and be touched by it in its own way."