Infection remains a significant challenge in healthcare and with medical devices, resulting in two million healthcare-associated infections reported annually in the U.S. alone. Researchers are seeking new antimicrobial materials and therapies to solve the infection challenges associated with biomaterials and devices without bacterial resistance. Nitric oxide (NO) is a new therapy to treat infection, inflammation, and thrombosis, and many materials have been studied to inhibit bacteria by doping NO donor molecules and releasing NO. However, this strategy has been limited by the leaching of the NO donors which delocalizes the NO release. Silicones are widely used in making medical devices and exploring antimicrobial silicones could benefit the existing medical device interfaces. Herein, we report the first NO-releasing silicone oil (SNAP–Si) that exhibits proactive antibacterial effects. Through a two-step reaction, S-nitroso-N-acetylpenicillamine (SNAP) was grafted to poly[dimethylsiloxane-co-(3-aminopropyl)methylsiloxane], and the resulting SNAP–Si oil contained 0.6 mmol g⁻¹ of SNAP and demonstrated storage stability at −20 °C for > 3 weeks. The SNAP–Si oil was infused in medical-grade silicone rubber (SR) surfaces, increasing the hydrophobicity of the SR interface. The SNAP–Si–SR samples released most of the NO payload in 24 h without SNAP leaching, and the highest release flux was around 3.8 × 10⁻¹⁰ mol min⁻¹ cm⁻² during the initial 1 h, followed by NO release at a therapeutic level for 6 h as measured using a chemiluminescence NO analyzer. SNAP–Si–SR also exhibited more than 66% and 94% reduction of viable Escherichia coli and Staphylococcus aureus on the surfaces after 3 h, respectively. Due to the easy synthesis, suitable NO release levels without leaching issues, simple infusion on a polymer surface, and antimicrobial effects, the SNAP–Si oil exhibited its potential use to create an antimicrobial medical device surface that can reduce infection challenges.