•At both testing points (i.e., immediate and delayed post-test), explicit instruction yielded better results for the learning of the form of the suffixes compared to implicit instruction.•Findings suggest that Grade 3 Spanish-speaking students formed an orthographic representation of the presented suffixes only after receiving explicit instruction.•Concerning the acquisition of suffix meanings, results from the multiple-choice task suggest that irrespective of how the suffixes were taught (implicit or explicit), there was a limited amount of overall suffix learning. The predominant form of learning seems to be instance-based, but there was little evidence of transfer to untrained words.•For the expressive task that assessed a deeper knowledge of the word, the results were significantly better following explicit instruction.•We suggest that the rich morphology of the Spanish language might provide students with ample oral morphological knowledge but given the orthographic characteristics of the language and the focus of the reading instruction, it may remain dormant until explicit instruction is provided. The purpose of this study was to compare the effects of implicit and explicit morphological analysis instruction in Spanish, a language characterized by high morphological complexity and relatively consistent letter–sound correspondences. For 3 days, 94 Grade 3 Spanish monolingual students (43 girls; Mage = 8.9 years) were trained on target words containing experimenter-designed suffixes consistent in form and meaning (e.g., the suffix -isba refers to a factory in words such as “botisba” a boot factory and “cajisba” a box factory). Explicit and implicit instruction differed in the attention given to the co-occurrence of the suffixes in the target words. One day (immediate posttest) and 1 week (delayed posttest) after training concluded, participants were tested on their learning of the suffixes’ form using a suffix identification task and meaning using a word definition and a multiple-choice task. Results of mixed-effects models showed that explicit instruction yielded better results for the learning of the form of the suffixes. Regarding meaning, across-condition differences were detected only in the word definition task; explicit instruction produced better results for both trained and transfer words. We discuss our findings in the context of the grain-size unit theory and examine the interplay between the language’s orthographic and morphological characteristics, considering their impact on classroom instruction.