A novel fluorescent probe 1 is reported here with ratiometric response to hydrophobic proteins (casein) or proteins with hydrophobic pockets (BSA, HSA) through hydrophobic interaction. Probe 1 underwent deprotonation in aqueous solution at pH 7.4 and emitted blue fluorescence at 436 nm. Upon the addition of BSA, HSA or casein, the aggregation-induced emission fluorescence of 1 at 518 nm was turned on. The fluorescence intensity ratio, I₅₁₈/I₄₃₆ was linearly related to the concentrations of these proteins. The detection limits for BSA, HSA and casein based on IUPAC (C_DL = 3S_b m⁻¹) were 16.2 μg mL⁻¹, 10.5 μg mL⁻¹ and 5.7 μg mL⁻¹, respectively.