In enzymology, phenylacetaldehyde dehydrogenase () is an enzyme that catalyzes the chemical reaction
The three substrates of this enzyme are phenylacetaldehyde, oxidised nicotinamide adenine dinucleotide (NAD<sup>+</sup>), and water. Its products are phenylacetic acid, reduced NADH, and a proton.
This enzyme belongs to the family of oxidoreductases, specifically those acting on the aldehyde or oxo group of donor with NAD+ or NADP+ as acceptor. The systematic name of this enzyme class is phenylacetaldehyde:NAD+ oxidoreductase. This enzyme participates in phenylalanine metabolism and styrene degradation.