A vehicle lower portion structure has: a tunnel portion disposed at a vehicle transverse direction central portion of a floor portion; a front side member whose rear portion is disposed at a vehicle lower side of the floor portion and a vehicle transverse direction outer side of the tunnel portion; a first member including a first horizontal wall that extends from the rear portion toward a vehicle transverse direction inner side, and a first vertical wall bent toward a vehicle upper side from the first horizontal wall; and a second member spanning an opening portion of the tunnel portion. The second member includes a second horizontal wall joined to the first horizontal wall, and a second vertical wall that is bent toward the vehicle upper side from the second horizontal wall, is disposed parallel to the first vertical wall, and is joined to the first vertical wall.