Officers located the Peugeot 308 near Valehouse reservoir in Tintwistle, just a short drive from the McDonald’s restaurant in Hattersley, Greater Manchester, where Emma Sillett was last seen on Tuesday lunchtime.
It is also only three miles from her home in the village of Dinting, Glossop.
The 41-year-old mother – described as white, 5ft 5in tall, and of slim build with straight brown hair – is believed to be with her young son Jenson Spellman.
According to reports, he has not been seen by staff at Simmondley Primary School since Tuesday morning.
Police said further searches were taking place in the area where the car was found.
Anyone with information that may help is asked to call 101.