In soil testing, assessing physical properties is essential for accurately characterizing sands. However, testing results can vary depending on the experimental procedures used and their implementation. A round-robin exercise facilitates the simultaneous analysis of the reproducibility and replicability of the standard methods used to characterize the properties of a specific material. This paper presents the outcomes of the first inter-laboratory testing initiative (i.e., a round-robin exercise) aimed at assessing the results variability of the physical characterization of a sandy soil. Guamo sand, widely utilized in local research and engineering projects in Colombia, was the focus of this study. 11 national academic laboratories participated in the program, conducting seven replicates of grain size distribution, solids specific gravity, and maximum and minimum void ratio tests. The data provided by all participants were analyzed and interpreted using statistical techniques. The results revealed significant differences between the data collected for each physical property, which can be attributed to the intrinsic variability of this sand’s natural origin and to the use of diverse testing procedures. These comparisons offer valuable practical insights into the discrepancies between the testing methodologies employed by the participants for soil characterization, and they constitute a comprehensive database for future research or practical applications.