Embodiments of the invention provide a method, system and computer program product for data duplication detection in an in memory data grid (IMDG). A method for data duplication detection in an IMDG includes computing a hash value for each binary data value in a key value pair of a partition in an IMDG. The method also includes generating a map including an entry for each unique computed hash value and one or more keys corresponding to binary data values of respective key value pairs from which the hash value had been uniquely computed. Thereafter, only those hash values in the map with multiple keys associated therewith are identified and binary data corresponding to the multiple keys of the identified hash values are reported as potential duplicate data in the IMDG.