A connector assembly that includes a first connector and a second connector which are configured to mate with each other, wherein the first connector includes: a housing that has a first receiving space to receive the second connector , a slider that forms in the first receiving space a second receiving space to receive the second connector , is held by the housing such that the slider is slidable in a direction intersecting a mating direction (F), slides in a first direction to cause the second connector to move in the mating direction (F) in which the first connector is mated to the second connector , and slides in a second direction opposite to the first direction to cause the second connector to move in a direction opposite to the mating direction (F), wherein the connector assembly includes, on an inner wall of the slider and an outer wall of the second connector , backlash restraining configurations that abut against each other at the time of mating completion to restrain backlash between the first connector and the second connector , characterised in that the backlash restraining configurations include: a first protrusion that is provided on the inner wall of the slider so as to protrude in an inside of the second receiving space, and a second protrusion that is provided on the outer wall of the second connector so as to protrude outward, and, at the time of mating completion, presses the first protrusion in a direction to expand the second receiving space so as to cause the slider to abut against an inner wall of the housing . a housing that has a first receiving space to receive the second connector , a slider that forms in the first receiving space a second receiving space to receive the second connector , is held by the housing such that the slider is slidable in a direction intersecting a mating direction (F), slides in a first direction to cause the second connector to move in the mating direction (F) in which the first connector is mated to the second connector , and slides in a second direction opposite to the first direction to cause the second connector to move in a direction opposite to the mating direction (F), wherein the connector assembly includes, on an inner wall of the slider and an outer wall of the second connector , backlash restraining configurations that abut against each other at the time of mating completion to restrain backlash between the first connector and the second connector , characterised in that the backlash restraining configurations include: a first protrusion that is provided on the inner wall of the slider so as to protrude in an inside of the second receiving space, and a second protrusion that is provided on the outer wall of the second connector so as to protrude outward, and, at the time of mating completion, presses the first protrusion in a direction to expand the second receiving space so as to cause the slider to abut against an inner wall of the housing . a first protrusion that is provided on the inner wall of the slider so as to protrude in an inside of the second receiving space, and a second protrusion that is provided on the outer wall of the second connector so as to protrude outward, and, at the time of mating completion, presses the first protrusion in a direction to expand the second receiving space so as to cause the slider to abut against an inner wall of the housing . <EOS>