This research aims to determine the contributing factors of information security investment by developing a theory-based conceptual model using Partial Least Square techniques to analyze the data collected from 500 IT decision-makers in Vietnamese small and medium sized businesses. The findings from the conceptual model, which is based on Technology-Organization-Environment framework, suggests that the drivers of organizational intention to invest in information security include the organization’s internal information, size, perceived IT benefits and manager’s knowledge about information security. By understanding more about the contributing factors of information security investment, practitioners could focus on such factors to make rational investment decision and improve their defense against the emerging cyber-crimes. On the other hand, the authors also hope to fill in the existing gap of information security management research area in which there are few studies investigating the drivers of information security investments.