Abstract: Crack in any structure changes its natural frequencies. Therefore it is possible to determine the location and depth of crack by measuring its natural frequency changes. In this study, the application of MCOA numerical method for open edge-crack detection in an Euler–Bernoulli cantilever beam is proposed. The crack is modeled by a torsional spring, the coefficient of which is calculated using the crack dimensions. The objective function is the weighted squares difference of the measured and calculated natural frequencies. The results of the numerical simulations and experimental tests reveal high accuracy in detecting the location and depth of the crack.