The cross sections of 237Np and 238Np are important for accurate modeling and simulation of 238Pu in the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory (ORNL). Uncertainties in these cross sections can impact the ability to predict and optimize the target design and loading for 238Pu production targets. The effective capture cross section of 237Np in the location of pneumatic tube 1 in HFIR was measured as a first step in the measurement of the 238Np capture and fission cross sections. This paper describes the flux measurements, 237Np experiments, and data analysis of the 237Np capture cross section in HFIR.