The role of morphological processing has been shown to be highly relevant in learning to read. However, there is little evidence on the processing of derivational suffixes from a developmental perspective. The aim of this study is to assess the developmental emergence of suffixes as meaningful processing units in word recognition. To that aim, 96 children from fourth, fifth and sixth grade, as well as adults, took part in a masked priming lexical decision task (go/no-go version). Complex and simple words were primed by other words sharing the suffix (as in lechero/milkman/-> jornalero/laborer/) and word ending (as in araña/spider/->España/Spain/) or by words not sharing an ending (surfista/surfer/->jornalero/laborer/; carpeta/folder/->España/Spain/). Results in adults replicate previous studies by showing that only the related condition of complex words elicits a significant facilitation (see Duñabeitia, Perea, & Carreiras, 2008). With respect to children, only sixth graders generated a similar pattern to adults. Children in fourth and fifth grade showed no morphological effect. Our data reveal a progressive sensitivity to derivational suffixes in visual word processing. Results are interpreted from a developmental perspective of current findings on morphological processing.