Police said the motorhome was parked on the Belgrave-Gembrook Road, Emerald, when it rolled down the street around 10am today.
The motorhome hit a woman pushing a pram with a child inside before crashing into the verandah of a store.
The 70-year-old Emerald woman sustained serious injuries and was airlifted to hospital.
The young child inside the pram was not injured, and no one in the store was injured, police said.
The Victorian SES also responded to the incident, which reportedly happened directly opposite the Emerald unit on the Belgrave-Gembrook Road.
“(Our) units responded to reports of a mini-bus into a structure,” a spokesperson from Vic SES said.
”The VICSES crew is assisting with patient and scene protection in support of Ambulance Victoria.
“The VICSES crew remain on scene and will also assist with temporary stabilisation to the building structure.”