Helical anchors are installed in the field by means of torque application, and during the installation, the soil traversed by the helices experiences torsional and vertical shearing. Considering that the uplift capacity of helical anchors depends mainly on the shear strength of the disturbed soil mass above the helices, an evaluation of the effect of the soil modification on the anchor capacity, caused by the installation procedure, is helpful to the understanding of helical anchor performance. The present investigation was conducted to examine this effect of installation on the uplift capacity of helical anchors in sand by centrifuge model tests. The influence of helix diameter and of sand’s initial density on the degree of loss in the helix uplift bearing capacity, due to sand disturbance, were evaluated. In addition, the results indicate that dimensionless pull-out capacity factor, typically used to estimate helical anchor capacity, varies with the helix diameter.