Background: To determine whether referred women experience differences in diagnostic workup at non-blinded or blinded double reading of screening mammograms. Methods: We included a consecutive series of respectively 42.996 and 44.491 screens, double read either in a non-blinded or blinded manner between 2009 and 2011. This reading strategy was alternated on a monthly basis. Results: The overall ultrasound-guided core needle biopsy (CNB) rate and stereotactic CNB (SCNB) rate per 1000 screens were higher at blinded than at non-blinded reading (7.5 vs 6.0, P = 0.008 and 8.1 vs 6.6, P = 0.009). Among women with benign workup, these rates were higher at blinded reading (2.6 vs 1.4, P <0.001 and 5.9 vs 4.7, P = 0.013). The benign biopsy rates were higher at blinded double reading (P <0.001), whereas the positive predictive value of biopsy did not differ (P = 0.103). Conclusions: Blinded double-reading results in higher overall CNB and SCNB rates than non-blinded double reading, as well as a higher benign biopsy rate.