Platelet Activating Factor Acetylhydrolase Ib3(PAFAH1B3) is an acetylhydrolase that catalyzes the removal of an acetyl group from the glycerol backbone of platelet-activating factor. The encoded enzyme is a subunit of the platelet-activating factor acetylhydrolase isoform 1B complex, which consists of the catalytic beta and gamma subunits and the regulatory alpha subunit.

This complex functions in brain development. A translocation between this gene on chromosome 19 and the CDC-like kinase 2 gene on chromosome 1 has been observed, and was associated with mental retardation, ataxia, and atrophy of the brain. Alternatively spliced transcript variants have been described.