Local scour is the major cause of bridge water damage. The sediment in the riverbed around the pier is eroded and transported by water flow, leading to a loss of bridge foundation stability. In this study, a horn-shaped collar was proposed to mitigate local scour around bridge piers. The three design parameters (bottom diameter, vertical height, and curvature shape index) of the horn-shaped collar were studied under clear water condition, and the number of experimental tests was reduced to 25 by using Taguchi’s method. Main effect analysis was used to determine the optimum design parameters for the horn-shaped collar. The results show that the three design parameters have a significant effect on the scour reduction capacity of the horn-shaped collar, with the bottom diameter of the collar making the greatest contribution. The optimum values for the bottom diameter, vertical height, and curvature shape index are 5D, 0.25D, and 4, respectively (D represents the diameter of the pier), and the optimized shape of the horn-shaped collar reduces the maximum scour depth around the pier by 100% compared to the unprotected case. Based on the experimental data, prediction equations are developed for the maximum scour depth protected by a horn-shaped collar.