Naomi Watts as Susan Carpenter, the mother of Henry and Peter Jaeden Lieberher as Henry Carpenter, the title character and Susan 's older son. Jacob Tremblay as Peter Carpenter, Henry 's brother and Susan 's younger son Sarah Silverman as Sheila, a waitress and Susan 's best friend Dean Norris as Glenn Sickleman, the police commissioner and Christina 's abusive stepfather Lee Pace as David Daniels, a neurosurgeon who operates on Henry Maddie Ziegler as Christina Sickleman, Glenn 's stepdaughter Tonya Pinkins as Janice Wilder, the school principal Bobby Moynihan as John, Susan 's and Sheila 's boss at the diner Geraldine Hughes as Mrs. Evans, Henry 's and Christina 's teacher Jackson Nicoll as Morris, a boy who bullies Peter
who played peter in the book of henry
Jacob Tremblay