I investigate the acquisition of affrication in Québec French (QF), where affricates are in complementary distribution with coronal stops, being realized before high front vowels and glides. Previous research on other languages shows that affricates are acquired before branching onsets, which supports the idea that complexity at the level of the segment is acquired before complexity at the level of the syllable (Lleó & Prinz, 1997). In contrast, I hypothesize that affricates are acquired after branching onsets in QF, as learners are required to understand the constraints on their distribution. I examine longitudinal data from two QF-speaking children for whom the acquisition of branching onsets has been previously analyzed (Rose, 2000). Results show that affricates are indeed acquired after branching onsets, consistent with the hypothesis. Overapplication errors indicate that children make generalizations about the phonological constraints on affrication from an early age, which is expected for the acquisition of rules.