Abstract We examined the effects of morpho-orthographic decomposition on complex word processing using a combination of masked priming and ERP recordings. The process of morpho-orthographic decomposition was primed by the prior presentation of complex non-words (formed by the combination a legal stem and legal affix, e.g. huntity, cornity, scanity) as prime stimuli. Targets were semantically transparent complex words (e.g., hunter), semantically opaque pseudocomplex words (e.g., corner), and simplex words (e.g., scandal) that contained the same stem as primes or a different stem (e.g., huntity-hunter vs. farmity-hunter). We found a large early (150–200ms) priming effect for transparent complex words only, followed by widely distributed priming effects between 200 and 300ms and more spatially focused N400 priming effects for all types of target. Furthermore, in the 150–200ms time-window, the ERP waveforms generated by pseudocomplex words patterned with those of complex words, both of which generated less negative-going waveforms compared with simplex words. In the N400 time-window, on the other hand, complex words differed from both pseudocomplex and simplex words. The results provide further support for early morpho-orthographic segmentation processes that operate independently of semantic transparency, and suggest that the output of these processes only affects the subsequent processing of truly complex words.