Amazon's stock spiked about 4 per cent to US$1,870 per share in after-hours trading following the news. The company's stock is up 57 per cent so far this year.
Amazon is going toe-to-toe with Apple and Google's parent company, Alphabet, to reach US$1t market capitaliation. Amazon's is currently US$861b. Apple, meanwhile, has a market cap of US$946b, while Alphabet's is US$877b.
Overall for the three-month period ending June 30, profits totaled US$2.5b, or US$5.21 per share, up from US$197 million, or 41 cents a share, a year earlier.
About half of the company's quarterly revenue came from its flagship e-commerce business, which delivered US$27.2b in the second quarter. But as online sales grew, so did shipping costs: Amazon spent nearly US$6b mailing out packages in the second quarter, a 31 per cent increase from a year ago.
"We're really pleased with the retail growth," Brian Olsavsky, Amazon's chief financial officer, said in a Thursday afternoon earnings call. "We think it's driven by the Prime program, as well as increased selection, particularly third-party selection."
The retail behemoth has been growing at breakneck speed as it expands into a number of new industries, including health care, advertising and movie production. Last month, Amazon made its first foray into the pharmacy business when it announced plans to buy PillPack, which sells pre-sorted medicine online.
Its purchase of Whole Foods Market last summer gave Amazon something it had long lacked: A nationwide network of physical stores. The company's brick-and-mortar stores generated US$4.31b in second-quarter revenue. Since taking over Whole Foods, Amazon has lowered prices and expanded same-day delivery in a bid to attract more shoppers to the grocery chain.
But Amazon's eye-popping growth has also led to increased scrutiny over the possibility that the company's market dominance gives it monopoly power. President Donald Trump has been a vocal critic of the company - and its founder's ownership of The Washington Post. Earlier this week, he lashed out again against Amazon on Twitter, saying that "many feel" there may be antitrust concerns related to the company.
Amazon's Prime membership program, which costs US$119 a year, now has more than 100 million members worldwide.
The quarterly results do not include sales from last week's Prime Day, the company-created discount event that now brings in billions of dollars for Amazon. This year, the company said it sold more than 100 million items during the 36-hour sale, though it did not disclose sales figures.