The study investigated internet addiction and mental health comorbidities among students of the University of Port Harcourt, Nigeria. Three research questions as well as three corresponding hypotheses guided the study. The study used the correlational research design. The population of the study comprised 23,288 students of the University of Port Harcourt, Nigeria. A sample of 286 students from the Faculty of Education were drawn for the study using the purposive sampling technique. Four instruments were used to collect data for this study. They include; Internet Addiction Scale (IAS), Anxiety Scale (AS), Beck's Depression Inventory (BDI) and Insomnia Inventory (II). The instruments were designed on a four point Likert scale of Strongly Agree (SA) =4, Agree (A) =3, Disagree (D) =2, and Strongly Disagree (SD) =1. The Cronbach Alpha reliability was used to establish the internal consistency reliability coefficients of 0.77, 0.97 and 0.69 respectively. Responses to the research questions were analyzed with mean, standard deviation and t-test statistics, while the hypotheses were analyzed with one way analysis of variance and t-test statistics. The findings of the study revealed that anxiety relate significantly to internet addiction among University of Port Harcourt students, whereas insomnia and depression did not. Based on the findings of the study it was recommended among others that school counselors should endeavour to organize periodic seminars and orientation programs to educate students on the effect of internet addiction on their academics and social behaviour