A new species of sect. Diffusa, Geranium pseudodiffitsum (Geraniaceae) found in Ecuador and Peru is described. The new species is morphologically most similar to G. diffusum. Leaves of G. diffusum are ±densely covered by small and appressed hairs on both surfaces, while in G. pseudodiffusum hairs are restricted to margin and nerves of the abaxial side and more rarely on nerves of the adaxial side. Additionally, G. pseudodiffusum has glandular hairs on the stems, pedicels, sepals, petioles, and sometimes on the leaf lamina, while in G. diffusum only eglandular hairs are present. A morphological comparison to related species, and a new key for the whole section is provided. In addition, a detailed description, distribution map, habitat and line drawing are provided for this new species.