Bilingual adults are faster in reading cognates than in reading non-cognates in both their first language (L1) and second language (L2). This cognate effect has been shown to be gradual: recognition was facilitated when words had higher degrees of cross-linguistic similarity. The aim of the current study was to investigate whether cognate facilitation can also be observed in bilingual children’s sentence reading. To answer this question, a group of Frisian–Dutch bilingual children (N = 37) aged 9–12 years completed a reading task in both their languages. All children had Dutch as their dominant reading language, but most of them spoke mainly Frisian at home. Identical cognates (e.g., Dutch–Frisian boek–boek ‘book’), non-identical cognates (e.g., beam–boom ‘tree’), and non-cognates (e.g., beppe–oma ‘grandmother’) were presented in sentence context, and eye movements were recorded. The results showed a non-gradual cognate facilitation effect in Frisian: identical cognates were read faster than non-identical cognates and non-cognates. In Dutch, no cognate facilitation effect could be observed. This suggests that bilingual children use their dominant reading language while reading in their non-dominant one, but not vice versa.