This article investigated the development of morphological awareness (MA) across three groups of students of Spanish as a second language (SSL) with different levels of proficiency. Four morphological assessment tasks on relational knowledge were designed in a simultaneous cross-sectional study that differed in two dimensions: complexity level (low vs. high) and type (detection vs. production). The results demonstrate that MA in Anglophone students of SSL shows an early development but that detection tasks improve faster than production tasks. Only productive tasks that are procedurally easy to perform improve over time, whereas more difficult productive tasks do not show better results across three consecutive years of Spanish courses. Limitations in the development of MA in SSL are therefore related to the use of morphological knowledge in difficult productive tasks but not in detection tasks or easier productive tasks. Results have implications for MA pedagogy and MA research