This is a Phase 2 open-label (all people know the identity of the intervention), multi-centric (conducted in more than one center), non-comparative, optional dose-titration study of tapentadol PR in Japanese participants with cancer pain. This study will consist of Screening period (3 to 7 days), Dose adjustment period (3 to 14 days), Fixed dose period (5 days) and Follow-up period (7 days). Tapentadol PR will be administered orally (taken by mouth; to be swallowed) twice daily before meal. For participants previously using opioids, the initial dose of tapentadol PR will be selected depending on the daily dose of opioid at the completion of Screening period. For opioid-naive (moderate to severe cancer pain that is not controlled adequately with non-opioid medications) participants, the initial dose of tapentadol PR will be 25 milligram (mg) twice daily. Participants will receive the same dose of tapentadol PR for the first 2 days of the dose adjustment period and from Day 3, the dose can be titrated as per the Investigator's discretion up to Day 14. After that participants will receive fixed dose regimen for 5 days at the same dose as that used at the end of the dose adjustment period. Efficacy will primarily be evaluated by sustained pain control for the 5 day fixed dose phase. Participants' safety will be monitored throughout the study.