A wearable blanket having a sack with an integrated crotch that keeps the upper portion of the garment in a fixed position on an infant wearer. The wearable blanket cannot twist on the wearer or slide up to the head, but maintains full freedom of leg movement. In one embodiment, the wearable blanket has a diagonal closure extending from an armhole to an opposing bottom quadrant. In another example embodiment, the wearable blanket has a perimeter closure, extending from an armhole around the sack perimeter. In another embodiment, the wearable blanket is a footed sleeper with a diagonal opening.