This un-blinded experimental study 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, 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 (FAS). Anxiety was measured using the State Trait Anxiety Inventory for Children (STAIC). When controlling for trait anxiety and opioid and non-opioid intake 1-4 h before the pain measures, 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 RM MANCOVA indicated no significant group differences in combined opioid and non-opioid use between the groups, or between times. Appropriately trained health care providers should use imagery to reduce post-operative pain following tonsillectomy and/or adenoidectomy in AS. Teaching parents about adequate home administration of analgesics may increase the effectiveness of imagery at home.