Reliability refers to the consistency of one outcome when the measurement is repeated. Sport scientists are aware of the importance of reliability and, consequently, a large number of single-center studies (performed in only one research center following specific protocols) have been conducted to evaluate the reliability of different testing procedures. Although single-center reliability studies are valuable, their findings could be compromised by the generally low sample size that can be gathered and restricted to the specific population and testing procedures used, reducing external validity. More robust information about the reliability of fitness tests could be obtained by pooling the data collected in independent research centers on a collaborative basis (multicenter reliability studies). This manuscript highlights the potential benefits of multicenter reliability studies and provides a number of recommendations for conducting multicenter reliability studies based on both a priori (researchers from different centers agree to collect data to address a specific question) and a posteriori (the data of published single-center studies are post-hoc combined) approaches.