In this article we focus on "false cognates", lexical items that have overlapping orthographic/phonological properties but little or no semantic overlap. False-cognate pairs were created from French (second language or L2) and English (first language or L1) items by manipulating the levels of morphological correspondence between them. Our aim was to test whether mismatches in morphological structure affected success on a low-frequency backward lexical translation task. Fifty-eight participants, divided into four groups (A-level; degree level; adult learners; bilinguals) were tested on monomorphemic items (simplex), polymorphemic items (complex), items whose morphological structure in French exceeded that of their English counterpart (mismatch), and control items. Translation success rate followed a uniform pattern: control > mismatch > simplex > complex. With respect to the false-friend effect, participant responses were also uniform: complex > simplex > mismatch. It is argued that an independent level of morphology explains these results.