While the theoretical models of morphological processing in Roman alphabets indicate prelexical activation, a model established in Korean suggests postlexical activation. To extend the model of Korean morphological processing, this study examined within-scriptal (Hangul-Hangul prime-target pairs) and cross-scriptal (Hanja-Hangul prime-target pairs) priming effects on the recognition of Sino-Korean compound words in Hangul as a function of adult readers' Hanja proficiency using priming lexical decision tasks. Experiment 1 (n = 54) examined the constituent morphemic effects of Hangul and Hanja primes, while Experiment 2 (n = 67) investigated morphemic decomposition in Hangul and Hanja primes. Participants with skilled Hanja proficiency showed robust constituent morphemic effects with both Hangul and Hanja primes in isolation, while less-skilled participants did not show the effects with Hangul and Hanja primes (Experiment 1). The skilled group showed efficient morphological decomposition in both within- and cross-script conditions. However, the less-skilled group did not show morphological effects in the cross-script condition but the same effect in the within-script condition (Experiment 2). The skilled group showed ortho-phonological inhibitory effects on Hangul recognition resulting from competitions among activated neighbors, but the less-skilled counterpart did not show the effect. Based on the findings of this study, two differing pathway models of morphological processing in Hangul are proposed for readers with different Hanja proficiency. Morphological processing in Sino-Korean compound words seems to be prelexical for skilled readers, whereas it is postlexical for less-skilled readers.