Abstract The objective of this research was to construct and develop a multi-level scale of ethical leadership, considered as both individual-level and group-level constructs. Data were collected by using the 62-item ethical leadership scale with 446 employees from 111 groups of private organizations in Bangkok. The ethical leadership scale was considered for its content validity by academic experts and its reliability was 0.89. The research found that ethical leadership had both an individual-level and a group-level of analysis; therefore, the framework for conducting multi-level construct validation was used. The results of confirmatory factor analysis indicated there were differences between factors of ethical leadership in the group-level (that had 1 factor) and the individual-level (that had 2 factors). Hence, ethical leadership had a group characteristic as Fuzzy composition. At the group-level testing, the convergent validity and construct reliability of this scale were accepted. The group-level construct reliability was 0.86 while individual-level construct reliabilities were 0.87 and 0.73 for each factor. Keywords: Ethical leadership, Multi-level analysis, Multi-level scale development, Construct reliabilit
