Previous studies on bilingual children have shown a significant correlation between first language (L1) and second language (L2) morphological awareness and a unique contribution of morphological awareness in one language to reading performance in the other language, suggesting cross-linguistic influence. However, few studies have compared advanced adult L2 learners from L1s of different morphological types or compared native speakers with advanced learners from a morphologically more complex L1 in their target-language morphological awareness. The current study filled this gap by comparing native English speakers (analytic) and two L2 groups from typologically different L1s: Turkish (agglutinative) and Chinese (isolating). Participants’ morphological awareness was evaluated via a series of tasks, including derivation, affix-choice word and nonword tasks, morphological relatedness, and a suffix-ordering task. Results showed a significant effect of L1 morphological type on L2 morphological awareness. After accounting for L2 proficiency, the Turkish group significantly outperformed the Chinese group in the derivation, morphological relatedness, and suffix-ordering tasks. More importantly, the Turkish group significantly outperformed the native English group in the morphological relatedness task even without accounting for English proficiency. Such results have implications for theories in second language acquisition regarding representation of the bilingual lexicon. In addition, results of the current study underscored the need to guard against the comparative fallacy and highlighted the influential effect of L1 experience on the acquisition of L2 morphological knowledge.