Purpose: Transformational leadership (TFL) has been identified by a number of studies as a positive force for business success. However, few studies have explicitly examined its influence on the cooperative employment relationship, such as frontline employees' voice in the workplace. Thus, this study conducts an empirical analysis of dual-level (i.e. group-focused and individual-focused) TFL and its effect on frontline employees' cooperative voice. Design/methodology/approach: This empirical study is based on data from a survey of 468 full-time frontline workers from 38 hotels in China. Findings: The empirical results revealed that both individual-level and group-level TFL are significantly associated with frontline employees' cooperative voice. Person–Organization value congruence and Person–Supervisor value congruence both act as mediators in the linkage between group-level TFL and employees' cooperative voice behaviors. The partial mediating role of Demand–Ability congruence on the relationship between individual-level TFL and cooperative voice is also established. Originality/value: First, this study investigates the dual-level effects of TFL on the cooperative voice behavior of frontline employees. Second, this study explores whether three dimensions of value congruence mediate the influence of TFL on the voice behaviors of employees.