In this paper, first we introduce the notion of a weighted \(\mathcal {O}\) -operator on Hom-Lie triple systems. Next, we construct an \(L_{\infty }\) -algebra whose Maurer-Cartan elements are weighted \(\mathcal {O}\) -operators. Consequently, we obtain the twisted \(L_{\infty }\) -algebra that controls deformations of a given weighted \(\mathcal {O}\) -operator on Hom-Lie triple systems. Subsequently, we introduce a cohomology theory for weighted \(\mathcal {O}\) -operators on Hom-Lie triple systems. As applications of our cohomology, we use the first cohomology group to classify infinitesimal deformations and we examine the obstruction class of an extendable n-order deformation. We conclude by introducing a new algebraic structure associated with weighted \(\mathcal {O}\) -operators, which we term the Hom-post-Lie triple system. Finally, we establish relationships between weighted \(\mathcal {O}\) -operators on Hom-Lie algebras and the induced Hom-Lie triple systems.