Labyrinth weir is an effective option to increase the discharge capacity. This increases the crest length for a given width and head. The efficiency of a labyrinth weir can be increased with an arced configuration by improving the orientation of the weir cycles to the approach flow and to further increase the weir crest length. In this study, the hydraulic performance of the arced labyrinth weirs is studied experimentally. The discharge coefficient is correlated to headwater ratio (Ho/P), downstream sidewall angle (α), and weir arc angle (Θ). Their effects on the weir efficiency are also investigated. The results indicate that by increasing the arc angle, the efficiency of the labyrinth weir can be increased up to 50%. In addition, the efficiency of the arced labyrinth weir can be increased up to almost 4.5 times of that of a linear weir. Finally, according to the limitations of present study, a method is proposed for designing arced labyrinth weirs.