Three species of Cassida Linné, 1758 from NE India are described as new to the science: Cassida mishmiensis sp. nov. (Arunachal Pradesh), C. atrosignata sp. nov. (Arunachal Pradesh) and C. pacholatkoi sp. nov. (Meghalaya). Type material of Thlaspida obenbergeri Spaeth, 1928 has been studied and a lectotype designation is given here. Thlaspida obenbergeri is transferred to the genus Cassida (comb, nov.) and a following new synonym is proposed: Cassida crucipennis Borowiec, 2003 = Cassida obenbergeri (Spaeth, 1928).