The disclosed computer-implemented method for expanding relevant search results in electronic discovery may include (1) creating a file-participant cluster that links a file within a data source to a set of participants that had interactions with the file, (2) determining that the file-participant cluster exceeds a threshold level of similarity relative to another file-participant cluster, (3) merging the file-participant clusters into a merged file-participant cluster that identifies files and participants linked by the file-participant clusters, (4) receiving, from a user involved in electronic discovery, a query to search the data source for files that match one or more search parameters, and then in response to receiving the query, (5) determining that the file linked by the file-participant cluster matches the search parameters, and (6) providing, to the user, a search result that identifies the merged file-participant cluster. Various other methods, systems, and computer-readable media are also disclosed.