A barley cultivar, designated BG 2020, is disclosed. The disclosure relates to seeds, plants, and derivatives of barley cultivar BG 2020, and methods for producing a barley plant by crossing BG 2020 with itself or another barley variety. The disclosure also relates to barley varieties or breeding varieties and plant parts derived from barley BG 2020, to methods for producing other barley varieties, lines, or plant parts derived from barley BG 2020, and to the barley plants, varieties, and their parts derived from the use of those methods. The disclosure further relates to hybrid barley seeds and plants produced by crossing barley cultivar BG 2020 with another barley cultivar. The disclosure relates to methods for developing other barley varieties or breeding lines derived from variety BG 2020, including cell and tissue cultures and haploid systems.