In preparation for deep extragalactic imaging with the James Webb Space Telescope, we explore the clustering of massive halos at z = 8 and 10 using a large N-body simulation. We find that halos with masses of 109-1011 h -1 M ☉, which are those expected to host galaxies detectable with JWST, are highly clustered with bias factors ranging from 5 to 30 depending strongly on mass, as well as on redshift and scale. This results in correlation lengths of 5-10 h -1 Mpc, similar to those of today’s galaxies. Our results are based on a simulation of 130 billion particles in a box of size 250 h -1 Mpc using our new high-accuracy ABACUS simulation code, the corrections to cosmological initial conditions of Garrison et al., and the Planck 2015 cosmology. We use variations between sub-volumes to estimate the detectability of the clustering. Because of the very strong interhalo clustering, we find that a medium-sized survey with a transverse size of the order of 25 h -1 comoving Mpc (about 13′) may be able to detect the clustering of z = 8-10 galaxies with only 500-1000 survey objects if the galaxies indeed occupy the most massive dark matter halos.