Metallic nanoparticles are increasingly studied for their biomedical applications due to their unique physicochemical and catalytic properties. Here, a broccoli-mediated gold/platinum nanohybrid (Au@Pt NH) was synthesized using an ultrasound-assisted green method with an aqueous extract of Brassica oleracea var. italica for multifunctional biomedical evaluation. XRD and TEM confirmed a crystalline nanohybrid with an average crystallite size of 7.56 nm and a mean particle diameter of 13.08 ± 7.58 nm. The broccoli extract produced no inhibition zones, whereas Au@Pt NH inhibited Staphylococcus aureus (18 mm), Staphylococcus epidermidis (21 mm), Escherichia coli (18 mm), Klebsiella pneumoniae (20 mm), and Candida albicans (21 mm). In vivo, Au@Pt NH accelerated wound healing, reaching 93.33% closure by day 7 compared to 75.84% (extract) and 62.18% (control), with complete re-epithelialization and organized collagen deposition. In streptozotocin-induced diabetic rats, oral Au@Pt NH (25 µg/mL) significantly reduced blood glucose levels, approaching near-normal levels by day 15, whereas the broccoli aqueous extract showed only moderate improvement. In vitro antioxidant test (DPPH) demonstrated potent scavenging (IC₅₀ 13.19 µg/mL for Au@Pt NH; 11.32% for extract) compared with ascorbic acid (21.82 µg/mL) and improved in vivo redox status (TOS 0.79 ± 0.58 µM H2O2 Eq/L; TAC 7.51 ± 1.0 mM ascorbic acid Eq/L; OSI 0.11 ± 0.08). MTT assays revealed selective cytotoxicity toward HepG2 cells (< 10% viability at 200–500 µg/mL; IC₅₀ 17.58 ± 4.51 µg/mL), whereas > 60% viability was observed in normal HDF cells at the same concentrations. In conclusion, broccoli-derived Au@Pt NH offers a multifunctional platform for antimicrobial activity, wound healing, glycemic control, oxidative stress modulation, and selective anticancer effects.