The tailgate storage case assembly is made of an elongated hollow storage compartment having a closed front end and an open rear end. A pivot bracket is mounted to the storage compartment near the front end for supporting the front end to the sidewall of a pickup truck box. The pivot bracket has a pivot joint therein for allowing an angular displacement of the hollow storage compartment about the pivot joint. The storage case assembly also includes a latch bracket mounted to the storage compartment near the rear end thereof for supporting the rear end to the sidewall. The latch bracket has a slide surface thereon for allowing the rear end of the hollow storage compartment to be displaced toward and away from the sidewall to define a clearance between a ramp being stowed in the storage case assembly and the tailgate post of the pickup truck.