A bottle warmer includes a flexible tubular sleeve having a closed lower end and an open upper end. The open upper end is to receive a bottle therethough, and the closed lower end is to receive a bottom of the bottle thereagainst. An elastic band is carried by a medial portion of the flexible tubular sleeve to secure the medial portion to an adjacent portion of the bottle, and permit the open upper end to be folded back adjacent the closed lower end to define a pocket. A chemical heat source element is to be received by the pocket for warming the bottle.