Background: Accurate nonword repetition (NWR) is contingent on many underlying skills, including encoding, memory and motor planning and programming. Though vowel errors are frequently associated with childhood apraxia of speech (CAS), several recent studies have found that children with developmental language disorder (DLD) produce high rates of vowel errors in NWR tasks. Aims: This retrospective analysis explored whether the overall frequency and types of vowel errors produced in NWR distinguish children with DLD, children with CAS, children with speech sound disorder (SSD) and children with typical development (TD). Methods and Procedure: We present data for 24 children (six per DLD, CAS, SSD and TD groups), ranging in age from 50-92 months. Children with DLD, CAS and SSD showed similar articulation scores and children with DLD and children with CAS showed similar expressive language scores. Total vowel errors, total monophthong errors, monophthong substitutions, diphthongization errors, total diphthong errors, diphthong substitutions and diphthong reduction errors were calculated by syllable length and group. Repeated measures analyses of variance were used to examine group differences. Outcomes and Results: Children with DLD and children with CAS produced a higher frequency of total vowel errors compared to children with TD. Children with DLD produced more total monophthong errors than children with TD. Children with DLD and children with CAS produced more total diphthong errors than children with TD. For children with DLD, these were characterised by diphthong substitutions. For children with CAS, these were characterised by diphthong substitutions and diphthong reduction errors. For all measures, error rates in children with SSD did not significantly differ from any of the other three groups. Conclusion: Preliminary evidence indicates that children with DLD and children with CAS both show high rates of vowel errors in NWR tasks and weaknesses in encoding and memory. For children with CAS, additional motor planning difficulties are associated with an increased likelihood to reduce diphthongs. Children with SSD show more mild processing difficulties than children with DLD and children with CAS, though they do not perform as well as TD peers. Future work should replicate and further specify the processing weaknesses that affect vowel accuracy in NWR tasks in a larger sample.