Background: Prosodic reading is one of the steps needed to achieve reading fluency. It is already known that English children develop their reading prosody from the earliest grades of primary school, showing the greatest improvement between first and second grade, but there are no Spanish studies of the development of reading prosody in the first years of school. Reading prosody may develop earlier in Spanish children as Spanish is a transparent language, which makes it possible to achieve high accuracy in the first year of learning to read. Method: We performed a longitudinal study, monitoring children from first to third grade. The children were asked to read aloud a text including declarative sentences containing high-frequency and low-frequency words and interrogative sentences; we analysed the usual prosodic variables (i.e., pauses, duration of different segments and pitch variations). Results: The results showed that younger readers made more and longer pauses and read less accurately. Moreover, the frequency words affected accuracy in all three grades, but only modified reading time in the first and second grades. We found no differences between the grades with respect to declarative sentences, but reading in all grades was influenced by word frequency, with a flatter final intonation. In the case of interrogative sentences, we found that first graders had a flatter melodic contour, whereas second graders tended to exaggerate the final change in intonation. Conclusions: Our results confirmed that reading fluency increases dramatically between first and second grade. Although Spanish has a transparent orthographic system, Spanish children seem to develop reading prosody similarly to children using opaque languages.