Background: People with language disorders (including developmental language disorder--DLD) often struggle to learn new words and, for young adults, this could affect their success in future work. Therefore, it is crucial to support their learning of career-specific vocabulary. However, little published evidence exists regarding the effectiveness of speech and language intervention for older adolescents and young adults with (developmental) language disorder (D)LD within a post-16 provision. Aims: To investigate whether for students with (D)LD in a post-16 environment, the addition of direct individual intervention from a speech and language therapist (SLT) teaching course-specific vocabulary leads to more progress than just in-course teaching on bespoke vocabulary measures. Methods & Procedures: A total of 28 college-aged students (11 female and 17 male) with (D)LD (aged 16.0-19.9) participated in a within-participant study comparing progress with explicit vocabulary intervention plus in-course teaching versus in-course teaching alone. The participants were assessed at four time points (3 months pre-intervention, immediately pre- and post-intervention, 3.5 months after intervention) using bespoke vocabulary assessments with an equal number of nouns, verbs and adjectives. All participants received one-to-one vocabulary intervention from their usual SLT for 30 min per week for 9 weeks. The intervention had four main components: (1) to identify intervention focus, (2) to recap previously taught terms (using an online flashcard program), (3) to explicitly teach new words using word maps to help with: creating definition and pictorial representation, identification of word class and investigation of phonological and morphological properties, and (4) to add new words, with their definition and pictorial representation to online flashcard program. Outcomes & Results: The results showed a stable baseline, then during the intervention term significant progress on words targeted only in lessons and significantly greater progress on words targeted both in lessons and SLT sessions. Progress was maintained for 14 weeks. Individuals with initially lower scores showed smaller intervention effects. In general, performance was higher on verbs and on the definition recognition task and lower on the production tasks, but all tasks improved with intervention. Conclusions & Implications: Direct one-to-one vocabulary intervention with an SLT can lead to significant gains in knowledge of course-specific terminology for college-aged students with (D)LD. The effectiveness of speech and language therapy services for this age group in a wider range of areas of language and social communication should also be investigated.