Here, we designed a series of LNA/DNA mixmers complementary to the ISS-N1, and evaluated their ability to induce exon inclusion in type I SMA patient fibroblasts. These AONs efficiently rescued the expression of SMN protein in the cultured cells. A single mismatch in AONs significantly decreased the exon inclusion efficacy, indicating that these AONs are highly specific to the target sequence. In addition, the LNA/DNA mixmer showed significantly higher efficacy than the all-LNA oligonucleotide with the equivalent sequence. Our results demonstrate that the LNA/DNA mixmers could be promising drug candidates suitable for in vivo studies to develop AON therapies to treat SMA.