Plot hole: Early in the movie, the principal from Precious' school buzzes Mary's apartment intercom to talk to Precious about alternative education. In order to hear what the teacher is saying Precious has to press the 'Listen' button, but occasionally the teacher can be heard speaking through the intercom even when Precious isn't holding the listen button.
Factual error: The movie takes place in 1987, but during the museum visit the main character is watching video from the Tiananmen Square uprising, which didn't occur until 1989. (00:52:40)
Continuity mistake: Just as Precious is running out of the deli with her stolen bucket of chicken, you can see that she has left her new journal and pen on the counter. Later, in her first day of school, she has the journal.
Character mistake: Early in the film in the scene in which Precious is in math class just before being called to talk to the principal, on the blackboard someone, presumably the teacher, has written REQUIRMENT, which is a misspelling of "requirement"
Other mistake: After Precious has her baby, Abdul, her school friends visit her in the hospital as her nurse, "John," is eating lunch with her. When John introduces himself to Precious' friends, he says he is a nurse's aide, and then later refers to himself as "Nurse John." When he stands up to leave the hospital room, you can see the word "NURSE" on his hospital ID badge pinned to his scrubs.
Continuity mistake: When Precious is in the Principal's office, the knot on her scarf changes in the close-ups.
Continuity mistake: Mongo throws the tin foil plate to the floor, but after that it keeps appearing and disappearing randomly on the table.
Character mistake: While Precious is in the hospital, her teacher is writing a response to Precious' journal entry in which Precious had written about her grandmother having referred to her as a "dog." In the note the teacher wrote, it says "Dear Precious, You are not a dog. You are a wonderful young women." instead of "You are a wonderful young WOMAN."
Continuity mistake: In Precious, the scene where Mary, Mrs. Weiss and Precious are discussing being reunited Mary's red lipstick is on in one shot, off in the next.
