We demonstrate that Tectaria cadieri (Tectariaceae) is a distinct species in Vietnam after long being placed under the synonymy of T. ingens. Morphologically, T. cadieri is similar to T. ingens, T. setulosa, and T. trichotoma in their large fronds (up to 0.8–2 m long), 3-pinnate laminae, fully free veins, and sori in two rows on ultimate segments. However, our observations show that T. cadieri differs from these species in the presence of linear, membranaceous stipe scales. Our analyses of five plastid regions (atpB, ndhF plus ndhF-trnN, rbcL, rps16-matK plus matK, and trnL-trnF) show that T. cadieri is not closely related to T. ingens, T. setulosa, nor T. trichotoma. Rather, T. cadieri is closely related to T. multicaudata, a morphologically distinct species with anastomosing veins. Along with a detailed description and illustrations for T. cadieri, we provide morphological comparisons and comments on the relationships between T. cadieri and morphologically similar species.