Phenyl isothiocyanate is an aromatic isothiocyanate. It participates in dehydration reactions of alcohols. It is widely used for synthesis of various biologically important heterocyclic compounds.

Derivatizing reagent for primary and secondary amines. Used in sequencing peptides by Edman degradation and in amino acid analyses by HPLC.

Phenyl isothiocyanate may be employed as a derivatization reagent for high-performance liquid chromatographic (HPLC) analysis of various amphetamine derivatives in body fluids for forensic purposes.
Phenyl isothiocyanate (PIT) modified with polyethylene glycol (PEG), can be used as a reagent for PEGylation of protein using human serum albumin as a model protein.