  The splashback radius of a dark matter halo, which corresponds to the first
apocenter radius reached by infalling matter and substructures, has been
detected around galaxy clusters using a multitude of observational methods,
including weak lensing measurements. In this manuscript, we present how the
splashback feature in the halo density profile affects galaxy cluster masses
derived through weak lensing measurements if it is not accounted for. We find
that the splashback radius has an increasingly large effect on group-sized
halos towards $M_{200m} \sim 10^{13.5} \mathrm{M_\odot}$. Depending on the
model and the radial scale used, the cluster/group masses can be biased low by
more than 0.1 dex. This bias, in turn, would result in a slightly lower
$\Omega_m$ value if propagated into a cluster cosmology analysis. The
splashback effect with group-sized dark matter halos may become important to
consider, given the increasingly stringent cosmological constraints coming from
optical wide-field surveys.
