Although the relationship between sound and meaning in language is arbitrary, reliable correspondences between sound and meaning have been found in natural language. These sound symbolic relationships affect word learning, but less is known about how sound symbolism affects online processing during learning or for well-learned stimuli. We use the visual world paradigm and an artificial lexicon featuring carefully controlled sound symbolic correspondences to examine the effects of sound symbolism on the online processing of novel and well-learned stimuli. Initially, participants chose novel shapes matching the sound symbolic properties of the word above chance, reliably fixating consistent shapes around word offset. As learning approached ceiling, accuracy and reaction time differences between matching and mismatching stimuli disappeared but a disadvantage in the online processing of mismatching stimuli persisted in the form of lagging target fixations. This suggests that sound symbolism affects the online processing of spoken stimuli even for well-learned words.