This RCT investigated the effectiveness of imagery, in addition to routine analgesics, in reducing tonsillectomy and/or adenoidectomy pain and anxiety after ambulatory surgery (AS) and at home. Seventy-three children, aged 7–12 years, were recruited from five AS settings. Thirty-six children randomly assigned to the treatment group watched a professionally developed videotape on the use of imagery and then listened to a 30-min audio tape of imagery approximately 1 week prior to surgery (T1). They listened to only the audio tape 1–4 h after surgery (T2) and 22–27 h after discharge from AS (T3). The 37 children in the attention-control group received standard care. Pain and anxiety were measured at each time-point in both groups. Measures of sensory pain were the Oucher and amount of analgesics used in AS and home; affective pain was measured with the Facial Affective Scale. Anxiety was measured using the STAI for Children. When controlling for trait anxiety and opioid and non-opioid intake 1–4 h before the pain measures, Multivariate Analysis of Covariance (MANCOVA) showed significantly lower pain and anxiety in the treatment group at T2, but not at T3. When controlling for trait anxiety, a two-way repeated measures MANCOVA indicated no significant group differences in combined opioid and non-opioid use between the groups or between times.