The Least Grebe ranges in length from 21–27 cm (approximately 8.25–10.5 inches, depending on the subspecies) and in weight from 112–180 g (3.95–6.35 oz). Like all grebes, its legs are set distant back on its body and it cannot walk well, while it is an excellent swimmer and diver. Small and plump, with a quite short, sharply-pointed beak and bright yellow eyes, it classically appears fairly dark all over.The breeding adult is brownish grey above with a darker blackish crown and throat. It has a brownish chest and pale underparts. It shows a white wing patch in flight. Non-breeding birds are paler with a pale throat, and immatures are paler and greyer than adults. Unlike all other members of its genus, it lacks any chestnut coloring on its neck.

