The reliable estimation of uplift capacity of plate anchors becomes necessary for the safe and cost-effective design of various structures against uplift loads. Uplift capacity studies have traditionally been conducted using semi-analytical methods based on plasticity theories, and the previous research has primarily focused on homogeneous soils and a linear failure criterion. Soils, in general, are nonhomogeneous and exhibit nonlinear shear strength behavior. The present study proposes a novel kinematic horizontal slice method within the context of plasticity theory to determine the vertical uplift capacity of various shapes of plate anchors in nonhomogeneous soils using the nonlinear power-law failure criterion. A linear variation of parameters such as initial cohesion, tensile strength, nonlinear coefficient, and unit weight with depth below the ground surface was considered. The effect of nonassociativity for a general nonlinear material has been examined. A detailed parametric study was conducted to explore the effects of various parameters on the uplift capacity of anchors. The results revealed that increasing initial cohesion while decreasing tensile strength, nonlinear coefficient, and unit weight with depth below the ground surface increases anchor uplift capacity, especially for three-dimensional cases. Anchor failure patterns were also investigated for a few parameter combinations. The results of this study were found to be more consistent with those developed in the literature for some specific cases.