Background: As infant disorganized attachment is a serious risk factor for later child psychopathology, it is important to examine whether attachment disorganization can be prevented or reduced. Method: In a randomized intervention study involving 130 families with 6-month-old adopted infants, two attachment-based intervention programs were tested. In the first program, mothers were provided a personal book, and in the second program mothers received the same personal book and three home-based sessions of video feedback. The third group did not receive intervention (control group). Results: The intervention with video feedback "and" the personal book resulted in enhanced maternal sensitive responsiveness (d = 0.65). Children of mothers who received this intervention were less likely to be classified as disorganized attached at the age of 12 months (d = 0.46), and received lower scores on the rating scale for disorganization than children in the control group (d = 0.62). In the book-only intervention group children showed lower disorganization ratings compared to the control group, but no effect on the number of infants with disorganized attachment classifications was found. Conclusion: Our short-term preventive intervention program with video feedback and a book lowered the rate of disorganized attachment. The effectiveness of our intervention documents the importance of parenting in the development of infant attachment disorganization.