Disclosed herein are antisense oligonucleotide sequences against IL-34 and methods for treating inflammatory diseases, such as inflammatory bowel disease, and/or fibrosis, associated with elevated activity or expression of IL-34. Also disclosed are pharmaceutical compositions containing an IL-34 antisense oligonucleotide useful for treating inflammatory diseases and/or fibrosis and manufacture of medicaments containing a disclosed IL-34 antisense oligonucleotide to be used in treating inflammatory diseases and/or fibrosis.