Purpose: The first purpose of this study was to investigate how children's knowledge of taught words and transfer words assessed 10 months after a morphological vocabulary intervention can be predicted by means of language measures taken before the intervention. The second purpose was to investigate whether and how immediate post-intervention measures can contribute to the prediction after pre-intervention measures are accounted for. Method: A secondary analysis of data from 87 participants in a trial of short- and long-term effects of a morphological vocabulary intervention for fifth-grade students with limited vocabulary was conducted. Students' knowledge of morphologically transparent taught words and transfer words was examined 10 months after the intervention. Pre-intervention and immediate postintervention measures of general vocabulary, knowledge of morphologically transparent words, morphological analysis of pseudowords, and metamorphological knowledge were evaluated as predictors. Results: By means of pre-intervention measures only, about 40% of the overall variance in students' knowledge of morphologically transparent words assessed at follow-up could be predicted. A good early classification of students with later relatively good or poor word knowledge could be obtained, especially for knowledge of transfer words. Furthermore, immediate post-intervention measures were found to add substantially to the prediction of overall variance in students' knowledge of morphologically transparent words at follow-up and to the correct early classification beyond the contribution from pre-intervention measures. In particular, pre- and post-intervention measures of knowledge of morphologically transparent words and morphological analysis of pseudowords in combination yielded a good classification of students with later relatively good or poor knowledge of transfer words. Conclusion: A good level of prediction of students' knowledge of morphologically transparent taught words and transfer words 10 months after a morphological vocabulary intervention can be provided by means of a combination of a few pre- and post-intervention measures of knowledge of morphologically transparent words and morphological analysis of pseudowords.