Context: Essential for adequate management of breakthrough cancer pain is a combination of accurate (re-)assessment and a personalized treatment plan. The Breakthrough Pain Assessment Tool (BAT) has been proven to be a brief, multidimensional, reliable, and valid questionnaire for the assessment of breakthrough cancer pain. Objectives: The aim of this study was to examine the validity and reliability of the Dutch Language version of the BAT (BAT-DL) in patients with cancer. Methods: The BAT was forward-backward translated into the Dutch language. Thereafter, the psychometric properties of the BAT-DL were tested, that is factor structure, reliability (internal consistency and test-retest reliability), validity (content validity and construct validity), and the responsiveness to change. Results: The BAT-DL confirmed the two-factor structure in 170 patients with cancer: pain severity/impact factor and pain duration/medication efficacy factor. The Cronbach's alpha coefficient was 0.72, and the intraclass correlation for the test-retest reliability was 0.81. The BAT-DL showed to be able to differentiate between different group of patients and correlated significantly with the Brief Pain Inventory. In addition, the BAT-DL was capable to detect clinically important changes over time. Conclusion: The BAT-DL is a valid and reliable questionnaire to assess breakthrough pain in Dutch patients with cancer and is a relevant questionnaire for daily practice.