Limited longitudinal studies have explored the development of reading, along with its predictors, in a language characterized by shallow orthography and a simple syllabic structure. In a 5-year longitudinal study, we investigated the development of reading skills in 327 Italian-speaking children (male: n = 180, 55%) from Grade 1 (mean age = 6.16 ± 0.28) to Grade 5 (mean age = 10.82 ± 0.31). We tested their reading performance at the end of each school year (Grade 1-5) and examined the impact of early cognitive factors (phonological awareness-PA, verbal short-term memory-vSTM, and non-verbal intelligence), environmental factors (socioeconomic status) as well as Grade 1 reading proficiency on subsequent reading development. A linear development of reading skills was found in both children classified as typical readers and those with reading disabilities. Non-verbal intelligence, PA, vSTM and reading proficiency at the end of Grade 1 predicted reading development throughout primary school (reading speed: R2-Intercept = 61.8%; R2-Slope = 12.9%, and reading accuracy: R2-Intercept = 40.1%; R2-Slope = 22.2%). The stability of reading performance across school grades highlights the significance of early reading skills as a marker and target for early intervention programs.