Nepotism has attracted growing scholarly and policy interest as it has proven resil¬ient to reforms in the civil service and other state institutions, undermining public confidence and the provision of public goods and services. Empirical studies on nep¬otism implicitly acknowledge that it is composed of two distinguishable attributes, a family tie, and its misuse, but most of them measure only one of them casting doubt on their conclusions. This paper provides a clear definition of nepotism, unpacks the concept, and evaluates the validity, reliability, and replicability of three measure¬ment strategies to capture it systematically: matching surnames, identifying family ties, and surveying perceptions. We illustrate each measure making use of a wealth of original data from the Mexican Federal Judiciary, offering practical tools for pro¬ducing an accurate diagnosis of the extent and depth of nepotism in an organization as a key first step to effectively address its causes or its consequences.Nepotism has attracted growing scholarly and policy interest as it has proven resil¬ient to reforms in the civil service and other state institutions, undermining public confidence and the provision of public goods and services. Empirical studies on nep¬otism implicitly acknowledge that it is composed of two distinguishable attributes, a family tie, and its misuse, but most of them measure only one of them casting doubt on their conclusions. This paper provides a clear definition of nepotism, unpacks the concept, and evaluates the validity, reliability, and replicability of three measure¬ment strategies to capture it systematically: matching surnames, identifying family ties, and surveying perceptions. We illustrate each measure making use of a wealth of original data from the Mexican Federal Judiciary, offering practical tools for producing an accurate diagnosis of the extent and depth of nepotism in an organization as a key first step to effectively address its causes or its consequences.