Smartphones have become an essential part of our modern society. Their popularity and ever-increasing relevance in our daily lives make these devices an integral part of our comput-ing ecosystem. Yet, we know little about smartphone users and their security behaviors. In this paper, we report our de-velopment and testing of a new 14-item Smartphone Security Behavioral Scale (SSBS) which provides a measurement of users' smart-phone security behavior considering both technical and social strategies. For example, a technical strategy would be resetting the advertising ID while a social strategy would be downloading mobile applications only from an official source. Initial evaluations of the scale also exhibit high reliability and good fit to a two-component behavioral model based on technical versus social protection strategies. This newly developed measure of smartphone security behavior is inspired by the theory of planned behavior and draws inspiration from a well-known scale of cybersecurity behavioral intention, the Security Behavior Intention Scale (SeBIS). The psychometrics of the scale were established by surveying 1011 participants. We believe this new scale and its measures can enhance the understanding of human security behavior for security researchers and HCI designers.