ABSTRACT Objective Alexithymia has been implicated as a risk factor for problematic substance use and other excessive behaviours including internet addiction . Impulsiveness has also been identified as a likely predisposing factor for excessive behaviours. However, as impulsivity is often elevated in alexithymia, the degree of independence of these factors in relation to excessive internet use is unclear. Method The present study assessed contributions of alexithymia, impulsivity and negative affect to variance in internet addiction symptoms in 116 internet-using female university students. Participants completed the following instruments online: demographics, Toronto Alexithymia Scale-20, Barratt Impulsiveness Scale-11, Internet Addiction Test and the Depression Anxiety Stress Scales-21. Results Measures were significantly intercorrelated in expected directions. Hierarchical regression indicated that although both alexithymia and impulsivity were highly significant predictors of internet addiction symptoms after controlling for demographic covariates, the contribution of alexithymia became nonsignificant after adding impulsivity to the model. The final model explained 37% of variance in internet addiction symptoms. Multiple mediation modelling indicated that both impulsivity and negative affect fully mediated the association of alexithymia with internet addiction symptoms. Conclusions Impulsivity and negative affect may account for the link between alexithymia and internet addiction symptoms in young women at university. KEY POINTS What is already known about this topic: Alexithymia and impulsivity have been linked to a variety of addictive behaviors including internet addiction. Alexithymia and impulsivity have been reported to independently predict excessive alcohol use in regression models. Alexithymia may reflect deficient interoception and corresponding poor internal awareness of overconsumption cues in alcohol use. What this topic adds: In female university students, alexithymia, impulsivity, and negative affect were significant positive predictors of internet addiction symptoms in a regression model. Alexithymia was no longer significant after adding impulsivity to the model. Multiple mediation modelling indicated that impulsivity and negative affect fully mediated the association of alexithymia with internet addiction symptoms.