A growing body of evidence supports that Internet gaming disorder (IGD) is considered as ‘behavioral addiction’ with neurobiological alterations. We have reviewed previous research into the clinical and neurobiological features of IGD, and suggest a flowchart for the comprehensive evaluation of IGD. Several self-rating screening tests based on Diagnostic and Statistical Manual of Mental Disorder, 5th edition (DSM-5) IGD criteria were developed. IGD is often comorbid with depressive disorder, social anxiety disorder, attention deficit/hyperactivity disorder (ADHD), and smartphone addiction. Individuals with IGD are prone to act impulsively and make risky decisions, especially in response to game-related cues. Functional neuroimaging results have shown altered functional activities in prefrontal cortex, cingulate cortex, superior temporal gyrus and nucleus accumbens (NAc). Structural neuroimaging demonstrated gray matter volume changes in prefrontal cortex and NAc, while showing white matter integrity disruption in thalamus and posterior cingulate cortex. There are few evidences on the attribution of specific genes to IGD. To evaluate IGD comprehensively, self-rating scales based on DSM-5 are useful, but a diagnostic interview by a clinician is more helpful to assess functional impairments of IGD. Presence of psychiatric comorbidities such as depressive disorder, social anxiety disorder, ADHD, and smartphone addiction should be evaluated. Neurocognitive tests that assess impulsivity, decision-making under risk, and cue-reactivity are helpful when planning individualized IGD treatment.