Toyota, which many analysts expected would scoot by GM in June to take the title, posted a sales decline of 21.4 percent.
In terms of vehicles sold, it was GM 265,937 to 193,234 for Toyota.
Both companies were hurt by a sluggish economy and poor sales of trucks and sport utility vehicles.
Earlier today, Ford reported a slide of almost 28 percent. Chrysler has yet to post its June results.