In the current study, the N,N',N''-(1,3,5-triazine-2,4,6-triyl)tris(1-phenylmethanimine) (MBSB) condensation product of melamine (triazine) and benzaldehyde was investigated as a mild steel corrosion inhibitor in a 0.5 M HCl. The ability of the synthesized tris-Schiff base to suppress corrosion was evaluated utilizing weight loss measurements and electrochemical techniques. The maximum inhibition efficiency of 94.78%, 93.99% and 93.80% was achieved using 100 ppm of MBSB in weight loss measurements, polarization, and EIS tests, respectively. It was observed that increasing inhibitor concentration enhanced inhibition performance, whereas increasing temperature lowered inhibition performance. The analyses demonstrated that the synthesized tris-Schiff base inhibitor followed the Langmuir adsorption isotherm, and the inhibitor was an effective mixed-type inhibitor having a low cathodic predominance. According to the electrochemical impedance measurements, the Rct values increased with the increase of inhibitor concentration. In addition, theoretical calculations using density functional theory (DFT) were performed to reveal the anticorrosion mechanism. The weight loss and electrochemical assessments were also supported by surface characterization analysis and show a substantial smoothness in the surface morphology.