The geometry of integrable nearly trans-Sasakian manifolds (NST-manifolds) is studied in this paper. In particular, we consider as NST-manifolds with an integrable structure, normal NST-manifolds, and NST-manifolds satisfying the condition N(2)=0. Local structure of such manifolds is also described. We give a classification of NST-manifolds of constant Φ-holomorphic sectional curvature, as well as satisfying the axiom of Φ-holomorphic planes. NST-manifolds with a completely integrable first fundamental distribution are discussed.