We examined whether French third- and fifth-grade children rely on morphemes when recognizing words and whether this reliance depends on word familiarity. We manipulated the presence of bases and suffixes in words and pseudowords to compare their contribution in a lexical decision task. Both bases and suffixes facilitated word reading accuracy and speed across all grades, even though the co-occurrence of a base and a suffix reduced the benefit associated to the presence of morphemes in third-grade children. Speed of pseudoword (i.e., unfamiliar word) reading was also influenced by base and suffix, and the combination of these units leaded to a high rate of false alarms. These results bring new evidence of morphological analysis in the reading of French familiar and unfamiliar words.