Internet gaming disorder (IGD) is a behavioral addiction that is gradually becoming a public health problem. We aimed to identify the behavioral characteristics of adolescents with IGD to promote early diagnosis and intervention. As impulsivity and risk taking are the most important traits of addiction, we used several representative methods, including a delay discounting task, a probability discounting task and the Barratt Impulsiveness Scale-11 (BIS-11), to measure the impulsivity and risk-taking tendency of adolescents with IGD and a comparison group. Consistent with previous findings on problematic Internet use (PIU), our results indicated that adolescents with IGD had a larger degree of delay discounting (i.e., more impulsive decision making), regardless of the outcome amount and valence, and higher scores on all three subscales of the BIS-11 than the comparison group. However, there was no intergroup difference in the probability discounting task. In general, the current research posits that impulsive decision making and personality traits, but not risk taking, might co-occur with IGD in adolescents.