A heat-shrinkable backseamed casing film comprises a first layer, a second layer, and a third layer, with the first and third layers being outer layers and the second layer being between the first layer and the third layer. The first outer layer serves as an inside casing layer, and comprises polyolefin; the second layer comprises polyester and/or polyamide; the third layer serves as an outside casing layer and comprises polyolefin, polystyrene, and/or polyamide. The second layer has a thickness of at least about 5% of a total thickness of the heat-shrinkable casing film. Alternatively, the first layer comprises polyolefin and has a surface energy level of less than about 34 dynes/cm; the second layer comprises a polyamide having a melting point of at least 300° F.; and the third layer comprises polyolefin, polystyrene and/or polyamide. A package comprises a cooked meat product within the backseamed casing. The second layer of the casing film prevents or reduces necking down on the forming shoe during backseaming. The backseamed casing is especially useful for cook-in applications.