When two companies merge, technical infrastructures change, formal security policies get rewritten, and normative structures clash. The resultant changes typically disrupt the prevalent security culture as well. In this paper we use ET Hall’s (1959) theory of cultural message streams to evaluate the disruptions in security culture following a merger. Findings from our analysis would be beneficial to researchers to theorize about security culture formulation during a merger. At a practical level decision makers would find the analysis useful for engaging in strategic security planning.