Medical treatment of subcutaneous bacterial abscesses usually involves systemic high-dose antibiotics and incision-drainage of the wound. Such an approach suffers from two main deficiencies: bacterial resistance to antibiotics and pain associated with multiple incision-drainage-wound packing procedures. Furthermore, the efficacy of high-dose systemic antibiotics is limited because of the inability to penetrate into the abscess. To address these obstacles, a treatment relying on laser-induced heating of gold nanoparticles embedded in an injectable silk-protein hydrogel is presented. Although bactericidal nanoparticle systems have been previously employed based on silver and nitric oxide, they have limitations regarding customization and safety. The method proposed here is safe and uses biocompatible, highly tunable materials: an injectable silk hydrogel and Au nanoparticles, which are effective absorbers at low laser powers such as those provided by hand-held devices. A single 10-minute laser treatment of a subcutaneous infection in mice preserves the general tissue architecture, while achieving a bactericidal effect, even resulting in complete eradication in some cases. The unique materials platform presented can provide the basis for an alternative treatment of focal infections.