A device for connecting a front frame of a turbojet engine nacelle to a fan casing includes a locking pin connected to a first assembly flange and a retaining flange that is movably mounted and has at least one opening. In particular, the locking pin has a shank passing through an orifice of a second assembly flange secured to the fan casing. The opening is crossed through by the shank of the locking pin and interacts with an end groove of said locking pin. When the retaining flange is in the unlocking position, the opening has dimensions larger than those of the shank of the locking pin, and when the retaining flange is in the locking position, the opening has dimensions larger than a thickness of the locking pin at its groove but smaller than an overall thickness of the shank of the orifice of the second flange.