A growing number of the concentrations that are notified to the European Commission involve online companies active in the collection and processing of big data. This article analyzes how these mergers are and should be assessed under EU merger control law. The author contends that although big data mergers should be closely scrutinized, as they may give rise to significant anticompetitive effects in some cases, the current EU competition law regime provides the necessary tools for the assessment of such transactions. Section II addresses the possible anticompetitive and procompetitive effects of big data mergers. Section III argues that there is no need for substantive reforms of the EU merger control rules and that the scope of the Commission's merger control proceedings should not extend to standalone privacy issues. Section IV concludes.