Abstract: This article reports on the implementation of diagnostic assessment in an advanced Spanish language program at the university level. Particular attention is given to the use of dynamic assessment practices as a way to assess language abilities, intervene in learning, and document learners' growth. Dynamic assessment is conceptually based on sociocultural theory, specifically on Vygotsky's notion of Zone of Proximal Development (Lantolf & Thorne, 2006; Minick, 1987). Assessment procedures conducted with third-year Spanish language majors are described with the purpose of illustrating the potential of dynamic assessment for second language learning contexts. Students took a five-part diagnostic test. Two parts of the test, the writing and speaking sections, were conducted following dynamic assessment procedures. A qualitative analysis of the results shows that dynamic assessment allows for a deeper and richer description of learners' actual and emergent abilities, which enables programs to devise individualized instructional plans attuned to learners' needs.