A method, system, and computer-readable medium is described for automatically identifying incongruous item packages, such as to detect incongruities in the items that are included as contents of the item packages and/or to identify incongruities in the packaging used for the item packages. In some situations, the automatic identification of incongruous packages includes initially automatically learning appropriate values for parameters of items (e.g., item weights and/or dimensions) based on automatically measured parameters of packages including those items. Those item values can then be used to estimate corresponding parameter values of sealed packages that contain those items, and to further identify incongruous item packages whose measured parameter values do not correspond to the estimated values for those parameters.