An LED lamp includes a planar base, an LED module mounted on the base, an envelope covering the LED module, and a lamp housing having a configuration like a lantern and defining a cavity. An annular receiving groove is recessed from a bottom face of the base. The LED module is attached on the bottom face of the base and surrounded by the receiving groove. The envelope includes a recessed body and an engaging flange extending outwardly from a periphery of the body. The engaging flange of the envelope is received in the receiving groove. The base, the LED module and the envelope are received in the cavity.