A vehicle side portion structure that includes: a rocker provided at a vehicle width direction outer side end portion of a lower portion of a vehicle body, the rocker extending in a vehicle front-and-rear direction; and a pillar that extends in a vehicle vertical direction, a lower end portion of the pillar being joined to the rocker. A bellows portion is provided at the lower end portion of the pillar. The bellows portion is provided at a vehicle upper side of a joining portion of the pillar with the rocker, and protrusions and recesses are formed in the bellows portion to alternate in the vehicle vertical direction.