An investigation room to interrogate packages and baggage at airports, based on a neutron-induced gamma-ray method, was designed using the MCNP5 Monte Carlo radiation transport code. A pulsed neutron generator source of interval time responses 10 μs turned on and 100 μs turned off was used for the investigation. Gamma-ray emissions in the forward, scattering angle of 90 deg, and backward directions were detected in the two cases of neutron generator (turned on/turned off). The detected data revealed that gamma rays in the forward direction have a signal-to-background ratio higher than the other positions. In addition, thermal neutron capture detected in the turned-off interval showed larger numbers of good signal-to-background ratio than that in the turned-on interval. The results show that the detection of gamma rays induced with a pulsed neutron source can be applied as a basic technique in airports to identify smuggled illicit materials.