A vehicular body front portion structure includes a cowl panel and a dash panel that extends below the cowl panel. The cowl panel has a concave body with an opening formed on the upper side when viewed from the side of the vehicle body. The concave body is formed from a front plate portion, a bottom plate portion, and a rear plate portion. The cowl panel is spot-welded to the front plate portion. A drainage groove that extends in the vehicle width direction of the vehicle body is provided in a front end portion of the bottom plate portion. An in-groove recessed portion, which is recessed from the drainage groove on the lower side of the concave body and which inhibits the dash panel from detaching from the cowl panel, is formed in the bottom of the drainage groove.