A connector 10 includes a male connector housing 14 having a retaining projection 19, a female connector housing 17 having an elastic lock arm 28 which is brought into retaining engagement with the retaining projection 19 when the male connector housing 14 is inserted and fitted into the female connector housing, and a fitting-ensuring member 13 which is brought into engagement with the elastic lock arm 28, retainingly engaged with the retaining projection 19, to hold the elastic lock arm 28 against elastic deformation. An abutment portion 38 is formed at one of the female connector housing 17 and the fitting-ensuring member 13, and during the movement of the fitting-ensuring member 13, the abutment portion 38 causes the fitting-ensuring member 13 to drop into the elastic lock arm 28.