Astragalus dinawarii Bidarlord & F. Ghahrem. (Fabaceae) is described as a new species based on material collected on the Talesh Mountains, northwestern Iran. This species belongs to a large bifurcating section, Astragalus L. sect. Incani DC. Morphologically, it is close to A. bukanensis Maassoumi & Podlech, A. diversus Podlech & Maassoumi, and A. dilutuloides Maassoumi, F. Ghahrem. & Bagheri, sharing several densely hairy leaflets and stipitate legumes. This species is easily distinguished from similar species by a set of both vegetative and reproductive characters such as size, shape, number of leaflets, shorter calyx, and longer legume stipe. A detailed description and comparisons with similar taxa, color images, distribution and habitat, and conservation status of the new species are provided.