Purpose In this study pupillometry was used to investigate the allocation of attentional resources associated with sentence comprehension in children with and without specific language impairment (SLI). Method Eighteen children with SLI (age: M = 6.4 years) and 18 typically developing (TD) children (age: M = 6.3 years) participated in the study. A sentence comprehension task was presented that comprised items designated as easy or hard. Easy sentences contained 4 or 5 words, and hard sentences contained 6 or 7 words. Results For the TD group, pupil size was significantly larger when comprehending hard sentences compared with easy sentences. There was no effect of sentence difficulty on pupil size in the SLI group. Comparisons between groups revealed pupil sizes for the SLI group were significantly larger than those for the TD group for easy sentences. There were no group differences for the hard sentences. Conclusion In TD children, pupillometry was sensitive to the attentional demands associated with sentence comprehension. Between-subjects comparisons indicated that the TD group allocated less attention than did the children with SLI for the easy sentences but not for the hard sentences. This study provides evidence of attentional differences between children with SLI and TD children under conditions of low processing demands.