Accurate and efficient determination of tigecycline is critical for pharmaceutical quality control and clinical therapeutic drug monitoring. Herein, silicon and nitrogen co-doped carbon dots (Si, N-CDs) with a high absolute quantum yield of 50.19% and excitation-independent emission were synthesized via a one-step hydrothermal method using trans-aconitic acid and N-[3-(trimethoxysilyl)propyl]ethylenediamine as precursors. The Si, N-CDs served as a fluorescent probe for tigecycline quantification, with the quenching mechanism of inner filter effect. Under optimized conditions, the quenching efficiency exhibited a linear response to tigecycline concentration over 1.5–25.0 µg/mL, with a detection limit of 1.1 µg/mL. The method was successfully applied to the determination of tigecycline in commercial pharmaceutical injections and spiked human plasma, achieving satisfactory recoveries. Bypassing the need for sophisticated instrumentation and complex sample pretreatment, this fluorescence platform offers a compelling combination of simplicity, rapidity, and cost-effectiveness, positioning it as a promising complementary tool for antibiotic quality control and therapeutic drug monitoring.