ABSTRACT We present Subaru/Faint Object Camera and Spectrograph and Keck/Deep Imaging Multi-Object Spectrometer medium-resolution spectroscopy of a tidally disrupting Milky Way (MW) globular cluster Palomar 5 (Pal 5) and its tidal stream. The observed fields are located to cover an angular extent of ∼17° along the stream, providing an opportunity to investigate a trend in line-of-sight velocities (Vlos) along the stream, which is essential to constrain its orbit and underlying gravitational potential of the MW's dark matter halo. A spectral fitting technique is applied to the observed spectra to obtain stellar parameters and metallicities (Fe/H) of the target stars. The 19 stars most likely belonging to the central Pal 5 cluster have a mean Vlos of −58.1 0.7 km s−1 and metallicity Fe/H = −1.35 0.06 dex, both of which are in good agreement with those derived in previous high-resolution spectroscopic studies. Assuming that the stream stars have the same Fe/H as the progenitor cluster, the derived Fe/H and values are used to estimate the possible Vlos range of the member stars at each location along the stream. Because of the heavy contamination of the field MW stars, the estimated Vlos range depends on prior assumptions about the stream's , which highlights the importance of more definitely identifying the member stars using proper motion and chemical abundances to obtain unbiased information of Vlos in the outer part of the Pal 5 stream. The models for the gravitational potential of the MW's dark matter halo that are compatible with the estimated Vlos range are discussed.