Introduction: For adequate pain treatment in patients with cancer, it is important to monitor and evaluate pain regularly. Although the numeric rating scale (NRS) is implemented in hospitals in the Netherlands, pain is still not systematically registered during outpatient consultations. The aim of this study was to assess whether home telemonitoring increases pain registration in medical records of outpatients with cancer. Methods: Patients with cancer were included in the intervention group (IG) when they visited the outpatient clinic. They received a short message service and an interactive voice response on their mobile phones 3 times a week, asking them to provide their pain score (NRS). When the reported NRS pain score was ≥5, a specialized oncology nurse adapted the pain treatment when necessary. Outcomes were compared to a control group (CG) without home telemonitoring. In both groups, medical records were analyzed and data on pain and analgesics were collected. Results: In each group, the medical records of 54 patients were analyzed on 3 consecutive outpatient visits. In the CG, pain registration or its absence was described in 60 visits (37.0%). In the IG, pain registration or its absence was reported in 83 visits (51.2%). Patients in the IG received a prescription for analgesics significantly more often (36/54 patients [66.6%]) than did patients in the CG (18/54 patients [33.3%]), P < 0.01). Conclusion: Home telemonitoring for patients with cancer significantly increases registration of pain and prescriptions of analgesics in outpatient medical records. Home telemonitoring helps to increase the awareness of pain and its management.