Highly stable Ag–Au triangular nanoplates and nanoframes were fabricated through well controlled galvanic reaction, which showed tunable localized surface plasmon resonance (LSPR) and efficient two-photon luminescence with the guarantee of high stability under both strong near infrared laser and tough ion-contained environments. The two-photon absorption cross section (6.34 × 104 GM) could reach double that of Au nanorods. As revealed by excitation wavelength dependent TPL spectra and the simulation of the localized electric field of the nanostructures, the TPL performance of the Ag–Au TNFs was possibly mainly determined by the matched LSPR absorbance and the Ag–Au alloys composition. The high stability and the strong TPL make the Ag–Au TNFs promising candidates for various nonlinear optical applications and further the understanding of the two-photon behavior of noble metals.