Objective: Decoy transfection is a significant methodology for suppressing gene activation. The decoy can be synthesized easily; however, the major obstacle is the difficulty involved in effective in vivo delivery. Methods and Results: We used a fluorescein-labeled decoy to investigate the ultrasound-microbubble-mediated in vivo delivery in normal and injured mouse arteries. We showed that this approach could deliver the decoy into target tissues. In addition, we performed in vivo NF-ĸB decoy transfection into murine injured arteries using the ultrasound-microbubble method. Murine femoral arteries were injured using flexible wires to establish arterial injury. Pathologically, neointima/media areas in the NF-ĸB decoy transfection using ultrasound-microbubble group showed less than those in the control groups. Immunohistochemistry revealed that enhanced expression of inflammatory factors was observed in nontreated injured arteries, while the NF-ĸB decoy suppressed the expression. Conclusion: We revealed that ultrasound-microbubble delivery of the decoy is effective for transfection into target organs. We also indicated that NF-ĸB decoy transfection using this method has potential for the suppression of neointimal formation. Ultrasound-mediated transfection of the decoy can be beneficial for the clinical treatment of restenosis after coronary intervention and other cardiovascular diseases.