The online retail giant's website crashed just minutes into its much-hyped shopping holiday.
Millions of online shoppers were left frustrated as they stared at an error message on their screen.
Prime Day launched at 12 noon. The company said it was working to resolve the glitches and by later in the afternoon an increased number of customers were able to get on the site.
The shopping day was created to offer big discounts on a wide variety of products offered through Amazon.
The company created Prime Day in 2015 to mark its 20th anniversary and it has been a big success, with some analysts estimating that this year's event will generate $3.4 billion in sales worldwide, compared to $2.4 billion last year.
This year's Prime Day lasts an additional six hours.
The Associated Press contributed to this report.