Lasioderma serricorne (cigarette beetle) is a harmful stored-product pest that causes significant economic damage globally. Traditional synthetic pesticides pose environmental and health hazards, highlighting the need for sustainable alternatives. This research investigates the insecticidal and repellent effects of green-synthesized titanium dioxide nanoparticles (TiO₂-NPs) using Salvia officinalis (sage) extracts against L. serricorne. Fresh sage leaves from southern India were powdered and wet-milled with TiO₂ in ethanol (1:10) to produce TiO₂-coated sage nanoparticles, which were then incubated at 80°C. Adult L. serricorne were reared under controlled conditions (21–49°C, 50% RH, 12-hour light cycle). The insecticidal and repellent activities were tested at five concentrations (10–50 ppm) over 24, 48, and 72 hours, with neem azal as a positive control. Mortality data were analyzed with probit analysis to determine LC₅₀ and LC₉₀ at 95% confidence. Results showed concentration- and time-dependent effectiveness, with 50 ppm causing 76.83% mortality at 24 hours, 82.41% at 48 hours, and 95.72% at 72 hours. LC₅₀ values decreased from 34.400 ppm (24h) to 23.087 ppm (72h), and LC₉₀ values from 62.052 ppm to 44.744 ppm over time. Repellent activity at 50 ppm increased from 86.1% at 24 hours to 97.2% at 72 hours. All treatments differed significantly from controls (p < 0.05, DMRT), with high regression coefficients (R² = 0.986–0.992). The green-synthesized TiO₂-coated sage nanoparticles exhibit strong insecticidal and repellent effects that increase with concentration and exposure time, as indicated by decreasing LC₅₀ values, indicating sustained bioactivity. This eco-friendly nano biopesticide presents a promising alternative to synthetic chemicals for integrated pest management of stored products. Future studies should evaluate safety for non-target species, residual effects, and practical field applications to support commercialization.