The purpose of this study was to examine the mediating effect of intolerance of uncertainty and trait anger in relation to covert narcissism, which is predicted to affect adolescents internet addiction. Therefore, we used 239 data from 261 students collected from middle school students in Chungnam Province on December 11, 2017. The scale used consisted of covert narcissism, intolerance of uncertainty, trait anger, and internet addiction scale. The correlation analysis and mediating effects were verified using SPSS v.21 and Process Macro. The results of this study are as follows. First, there was a significant correlation between covert narcissism, internet addiction, intolerance of uncertainty, and trait anger. Second, both intolerance of uncertainty and trait anger was verified the dual mediation and partial mediation effects on between covert narcissism and internet addiction. This implies that covert narcissism of adolescents affects intolerance of uncertainty and it affects trait anger, so that lifts internet addiction tendency in the result. Therefore, it is necessary for intervention about intolerance of uncertainty and trait anger for adolescents with internet addiction. This result are implication for reviewing about relationship between intolerance of uncertainty, trait anger, covert narcissism, and internet
addiction.