This study aimed to evaluate the intensity and characteristics of pain, which was assessed at home by children with cancer or their parents using an app for mobile devices, for a 1-month poststudy enrollment. The participants of this observational prospective study were outpatients at the hematology/oncology department of an academic hospital in Italy, aged between 0 and 21 years, and receiving hospital-at-home care. Patients or their parents were asked to assess pain levels for one month at home using the Faces, Legs, Arms, Cry, and Consolability (FLACC) scale for patients aged <4 years and the Ospedale Pediatrico Bambino Gesù (OPBG) tool for patients aged 4 to 21 years. At study conclusion, parents were asked to complete a survey about their satisfaction with the app and to rate their child’s health in general, pain intensity, and frequency in the past 4 weeks. Of the 124 participants using the app, 94 (75.8%) reported pain (≥1) at least once during the 1 month. Of these, 53 (56.4%) at most reported mild pain, 33 (35.1%) moderate pain, and eight (8.5%) severe pain. The abdomen was identified as the most frequent (56.3%) pain site by patients aged 4 to 21 years. The child’s maximum pain intensity during the study period was negatively correlated with the parent’s report of the child’s health during the past month ( r = −.29, p < .01). Most of the participants were satisfied with the app and the information received about app usage. In conclusion, the app facilitated pain assessment and tracking in patients receiving hospital-at-home care.