<p>Residual tetracycline-class antibiotics (TCs) in animal-derived foods pose significant risks to human health, underscoring the demand for simple, low-cost, and on-site detection techniques. Herein, a ratiometric luminescent nanoprobe was developed based on Eu³⁺-modified zinc gallogermanate (ZGGO) nanoparticles. The addition of tetracycline (TC) enhanced the Eu³⁺ emission at 618&#xa0;nm via the antenna effect, while the intrinsic emission of ZGGO at 465&#xa0;nm was quenched through an inner filter effect. This dual-response enabled the quantitative detection of TC. The luminescence intensity ratio (<i>I</i>₆₁₈/<i>I</i>₄₆₅) showed excellent linearity with TC concentration in the range 0.2–70 µmol L^− 1 (R² = 0.9912), with a detection limit of 169.5 nmol L^− 1. Moreover, a smartphone-assisted portable platform was constructed for visual on-site analysis. The R/B value correlated linearly with TC concentrations (0.1 to 55 µmol L^− 1, R² = 0.9968), achieving a detection limit of 85.9 nmol L^− 1. The spiked recoveries measured by both methods in three fish samples ranged from 86.1% to 117.8%, and the results were reliably verified by the traditional high-performance liquid chromatography method, demonstrating the potential of the bimodal strategy for rapid screening of TCs in complex matrix samples.</p> Graphical abstract <p></p>