Increasing the levels of therapeutic proteins in vivo remains challenging. Antisense oligonucleotides (ASOs) are often used to downregulate gene expression or to modify RNA splicing, but antisense technology has not previously been used to directly increase the production of selected proteins. Here we used a class of modified ASOs that bind to mRNA sequences in upstream open reading frames (uORFs) to specifically increase the amounts of protein translated from a downstream primary ORF (pORF). Using ASO treatment, we increased the amount of proteins expressed from four genes by 30-150% in a dose-dependent manner in both human and mouse cells. Notably, systemic treatment of mice with ASO resulted in an ∼80% protein increase of LRPPRC. The ASO-mediated increase in protein expression was sequence-specific, occurred at the level of translation and was dependent on helicase activity. We also found that the type of RNA modification and the position of modified nucleotides in ASOs affected translation of a pORF. ASOs are a useful class of therapeutic agents with broad utility.