Helipoid gears are designed and manufactured for transmitting crossed-axes motion. The purpose of this study is to analyze the tooth geometry and contact patterns of Helipoid gears generated by helical shapers. Firstly, the mathematical model of Helipoid gear was developed based on the theory of gearing. According to the developed mathematical model, tooth contact analysis was utilized to predict the contact patterns, contact path, and transmission errors of Helipoid gears under various shaper cutter parameters and assembly errors. The effects of tooth number and the helix angle of the helical shaper on the tooth geometry and contact patterns were investigated. The contact patterns under various assembly errors were also explored. Finally, the contact patterns of crossed-axes Helipoid gear and helical gears with a crossing angle of 60 degrees are compared and discussed in this study.