An empirical study is conducted in this paper in order to evaluate the impacts of design teams on practices and performance of warranty, a signal of quality. Based on qualified 93 respondents from an investigation in 682 manufacturing companies in automobile, electronic and mechanic industries of China, involvements of design teams in warranty strategy makings are found to positively affect efforts of firms in warranty engineering practices, warranty service, organizational management and information technology application, so as to improve warranty performance of companies. However, participation of design teams has no significant influence on warranty cost management. Furthermore, firm size, firm industry, warranty type, and product diversity are selected as contingency factors, and impacts of them on warranty practices and performance are demonstrated.