•Novel naphthoic acid-based ionic liquid was synthesized and characterized.•“Functionalized ionic liquid-based non-organic solvent microextraction (FIL-NOSM)”.•Utilization of this ionic liquid enhanced recovery and avoided pH adjustment.•Central composite design was applied to optimize operational factors.•Low LODs and high recoveries for tetracyclines by FIL-NOSM method in foods. In traditional ionic liquids (ILs)-based microextraction, ILs are often used as extraction and dispersive solvents; however, their functional effects are not fully utilized. Herein, we developed a novel ionic liquid 1-butyl-3-methylimidazolium naphthoic acid salt (C4MIMNPA) with strong acidity. It was used as a mixed dispersive solvent with conventional C2MIMBF4 in “functionalized ionic liquid-based non-organic solvent microextraction (FIL-NOSM)” for determination of tetracycline antibiotics (TCs) in milk and eggs. Utilization of C4MIMNPA in FIL-NOSM method increased extraction recoveries (ERs) of TCs by more than 20% and eliminated the pH adjustment step because of its strong acidity. Under optimized conditions based on central composite design, the ERs of four TCs were 94.1–102.1%, and the limitsofdetection were 0.08–1.12μgkg−1 in milk and egg samples. This proposed method provides high extraction efficiency, less pretreatment time and requires non-organic solvents for determination of trace TC concentrations in complex animal-based food matrices.