Background. Different studies report co-existence among oral language impairments and reading difficulties. Most of these investigations have been conducted in languages with opaque orthographies such as English and their results cannot be completely extended to Spanish. Objective. To describes the relationship between oral language difficulties and reading process in Spanish as a language of shallow orthography in a sample of school children. Materials and methods. 58 children participated in two different measurement times: an initial oral language assessment was performed by applying the Preschool Language Scale (PSL-3) when the children were five to six years old, The second one was carried out three years later, using the Reading Processes Evaluation-PROLEC. Results. A causal relationship was observed between the assessed oral language variables (auditory comprehension and expressive communication) and the reading variables (decoding and comprehension). Reading performance in children identified as with presence of language delay differs significantly from the children without any delay, especially in regards to the decoding process. In the same way, a differential developmental rhythm was observed between those two groups coherently with the illusory recovery hypothesis. Conclusions. The results of this study suggest that oral language delay in Spanish can impact not only the decoding process but also the comprehension processes too. The relevance of this study consists on allowing new ways to explaining and linking components of oral language and reading, which favors the processes of diagnosis and intervention in speech and language therapy in both clinical and educational contexts.