In English grammar, the use of mass and count nouns affects the use of articles, plural marking, and agreement. Given that L2 learners usually have challenges in those domains in both the initial and subsequent stages of L2 acquisition, this study investigated how Turkish L2 learners of English treat mass and count nouns, as well as object mass nouns and mass/count flexible items, since conceptualizing a noun in a certain way may lead learners to use those nouns with different morphosyntax. Using a quantity judgment task adapted from Barner and Snedeker (2005), the researcher investigated to what extent Turkish L2 learners of English based their quantity judgments on cardinality or amount in evaluating substance mass nouns, object mass nouns (e.g., furniture), count nouns, and mass/count flexible nouns. The study also addressed the issue of first language transfer in L2 English in this domain. The results showed that L2 learners treated substance mass nouns, count nouns, and flexible mass/count nouns with count syntax in a target-convergent manner, but they differed from native speakers in object mass nouns and mass/count flexible items with mass syntax.