This study assessed the effects of multi-sensory training on the understanding of the alphabetic principle in kindergarten children from low socio-economic status families. Two interventions were compared, called HVAM (visual and haptic exploration of letters) and VAM (visual exploration of letters). The interventions were conducted by either researchers or teachers. Results showed that performance in the letter recognition task and in the initial phoneme identification task were higher after HVAM training than after VAM training in kindergarten. Moreover, pseudo-word decoding scores improved more after HVAM training than after VAM training in first grade. This delayed effect on decoding was explained by the children's poor performance on some language skills necessary for reading acquisition. Visuo-haptic exploration enables the children first to increase performance on letter knowledge and initial phoneme awareness and then allowed better decoding skills. No differences were found between the interventions conducted by researchers and those conducted by teachers.