We have examined pressure effect on the self-trapped states of the amide-I vibrational mode(N‒C˭O stretching) in crystalline acetanilide (C6H5NHCOCH3) by means of Raman spectroscopy. The pressure dependences of the spectral position and intensity are interpreted by taking into account the changes in both inter-molecular forces and intrachain dipolar couplings. In addition, a new self-trapped state is observed upon cooling in hydrostatic pressure above ∼ 2 GPa.