Recent studies focused on the influence of orthographic processing on reading and spelling performance. It was found that orthographic processing is an independent predictor of reading and spelling performance in different languages and children of different ages. This study investigated sensitivity to orthographic regularities in German-speaking children (N = 31) prior and during formal reading and spelling instruction. In addition, the relationship between sensitivity to orthographic regularities and reading and spelling performance was explored. Two aspects of children's sensitivity to orthographic regularities (sensitivity to frequent double consonants and sensitivity to legal positions of double consonants) were measured with a nonword forced choice task. The results show that sensitivity to orthographic regularities improved significantly from kindergarten to first grade. Moreover, children's sensitivity to orthographic regularities at the end of first grade accounted for a significant amount of unique variance in their reading and spelling performance. These results suggest that orthographic sensitivity on a sublexical level is important for the development of reading and spelling skills.