The sound of words has been shown to relate to the meaning that the words denote, an effect that extends beyond morphological properties of the word. Studies of these sound-symbolic relations have described this iconicity in terms of individual phonemes, or alternatively due to acoustic properties (expressed in phonological features) relating to meaning. In this study, we investigated whether individual phonemes or phoneme features best accounted for iconicity effects. We tested 92 participants' judgements about the appropriateness of 320 nonwords presented in written form, relating to 8 different semantic attributes. For all 8 attributes, individual phonemes fitted participants' responses better than general phoneme features. These results challenge claims that sound-symbolic effects for visually presented words can access broad, cross-modal associations between sound and meaning, instead the results indicate the operation of individual phoneme to meaning relations. Whether similar effects are found for nonwords presented auditorially remains an open question.