Tyrosinase (TYR) is a key rate-limiting enzyme involved in enzymatic browning in foods, and natural TYR inhibitors with clear mechanisms are important for food preservation. To clarify the inhibitory effect and molecular mechanism of cinnamaldehyde (CA) against TYR, L-3,4-dihydroxyphenylalanine (L-DOPA) was used as the substrate in this study. Enzyme activity assay, inhibition kinetics, fluorescence spectroscopic analysis, thermodynamic analysis, molecular docking, and Cu²? intervention experiments were performed to evaluate the effects of CA on TYR activity, binding behavior, and conformational changes. CA inhibited TYR activity in a concentration-dependent manner, with an IC?? value of 0.37 mg·mL?¹ and an inhibition constant of 20.02 mmol·L?¹. The inhibition type was identified as reversible competitive inhibition. Fluorescence analysis showed that a stable CA-TYR complex was formed mainly through static quenching, accompanied by changes in the microenvironment around Tyr and Trp residues. Thermodynamic analysis indicated that hydrophobic interaction might be the main driving force for cinnamaldehyde-tyrosinase binding. Molecular docking simulation suggested that cinnamaldehyde could enter or approach the active cavity of tyrosinase and interact with residues including His263, Phe264, and Val283.Cu²? intervention experiments showed that, with increasing external Cu²? molar concentration, the inhibition rate of CA against TYR decreased from 55.91% to approximately 16.00%. CA could reduce TYR activity by competitively interfering with substrate binding and altering the microenvironment around Tyr and Trp residues. The Cu²? intervention results further suggested that this inhibitory effect might be associated with copper-related processes near the active center of TYR. This study provides a theoretical basis for the development of CA as a natural antibrowning active compound.