Heritage speakers are an increasingly significant demographic in the US, representing approximately 22 percent of the population and 29 percent of the school-age population (Bowles, 2022). Language instructors often find these learners have difficulties with reading abilities in the heritage language. Addressing this challenge is crucial to ensure reading development in the heritage language. One way to develop reading ability in Portuguese is to take advantage of the lexicon's nature (Nation & Bauer, 2023). The ability to reflect upon and manipulate morphemes and employ word formation rules in one´s language to construct meaning is called morphological awareness (Kuo & Anderson, 2006; Carlisle, 2000), and its bidirectional correlation to reading comprehension has been an area of intense research. Most of the research on the bidirectional impact of morphological awareness on reading comprehension has been conducted with L1 monolingual English children (Carlisle, 1988, 1995, 2000; Kirby et al., 2011). Some studies have been undertaken with second language learners and bilingual children (Kieffer & Lesaux, 2007; Zhang & Koda, 2011). Studies on morphological awareness and reading comprehension in L1 Portuguese with children can be found in (De Freitas & Mota, 2015; Guimarães & Mota, 2016; De Freitas et al., 2018). Morphological awareness and reading comprehension have also been investigated in European Portuguese adults (Gonçalves et al., 2021). However, there are no studies of the bidirectional impact of morphological awareness in reading comprehension with adult heritage Portuguese learners inserted in a college setting studying Portuguese. This research fills this gap with adult heritage learners from Brazilian and European Portuguese. Two morphological awareness tasks were developed to test heritage learners’ ability to decompose and derive complex words. Three reading comprehension tasks were designed to test specific abilities: recalling the main idea, relevant details and inference, understanding text structure awareness/discourse organizations, and summarizing. The results show a positive correlation between morphological awareness and these specific reading comprehension abilities in heritage Brazilian and European Portuguese learners.