Models of irregular word reading that take into account both child- and word-level predictors have not been evaluated in typically developing children and children with reading difficulty (RD). The purpose of the present study was to model individual differences in irregular word reading ability among 5th grade children (N = 170), oversampled for children with RD, using item-response crossed random-effects models. We distinguish between 2 subtypes of children with word reading RD, those with early emerging and late-emerging RD, and 2 types of irregular words, "exception" and "strange." Predictors representing child-level and word-level characteristics, along with selected interactions between child- and word-characteristics, were used to predict item-level variance. Individual differences in irregular word reading were predicted at the child level by nonword decoding, orthographic coding, and vocabulary; at the word level by word frequency and a spelling-to-pronunciation transparency rating; and by the Reader group × Imageability and Reader group × Irregular word type interactions. Results are interpreted within a model of irregular word reading in which lexical characteristics specific to both child and word influence accuracy.