This paper claims that, under the Chilean Civil Code, good faith underpins the whole process of implication of contractual terms when a valid contract contains omissions that engender contractual gaps. This is the case regardless of whether the substance of the implied term is defined by the legislator, custom or by judges. Such an approach offers a unitary and coherent treatment for the entire process of construction of implied terms, which provides judges with institutional guidance to exercising their power to fill contractual gaps grounded in good faith, thus reducing the risk of judicial arbitrariness.