The aim of this study is to research concircular curvature tensor of nearly cosymplectic manifolds with generalized Tanaka-Webster connection. With this study, we have focused on the important curvature properties of nearly cosymplectic manifolds equipped with Tanaka-Webster connection. Also, based on these curvature properties, we have defined the concircular curvature tensor with respect to the generalized Tanaka-Webster connection. Then, we emphasized the properties that concircular curvature tensor of nearly cosymplectic manifolds with Tanaka-Webster connection provides in case of flatness, ?-concircularly flatness, ?-concircularly semisymmetric.