In the present paper, we examine the literature studying relations between problematic smartphone use (PSU) and anxiety symptom severity. We first present background on the health advantages and disadvantages of using a smartphone. Next, we provide caveats in distinguishing healthy smartphone use from unhealthy PSU, and we discuss how PSU is measured. Additionally, we discuss theoretical frameworks explaining how some people develop PSU, including Uses and Gratifications Theory, and Compensatory Internet Use Theory. We present our own theoretical model of how PSU is specifically related to anxiety. We discuss and review mental health constructs associated with PSU severity, based on prior literature. Next, we systematically review the research on PSU severity in relation to anxiety symptoms, given the recent growth of studies on this research question. Finally, we offer implications and recommendations for future research in this area.