Amazon.com Inc. said its profit fell sharply in the third quarter, sending its share price down, as the company continued to spend heavily in its push to offer Prime customers one-day shipping.

The company’s third-quarter profit fell 26% from a year ago to $2.1 billion and missed analysts’ consensus estimate of $4.59 a share, according to FactSet. In the last quarter, the company ended its quarterly profit streak and missed analyst expectations.

Revenue rose 24% to $70 billion—better than analysts’ estimates—compared with a 20% increase three months earlier. The third quarter included Prime Day, a July shopping event created to sign up new Prime subscriptions by offering steep sales for members.

Amazon’s profit miss sent shares down more than 7% in after-hours trading Thursday. Before the late-afternoon report, the stock was up nearly 16% this year, giving the company a market value of around $881 billion.

Amazon’s world-wide shipping costs jumped 46% to $9.6 billion from the previous year as the company processes higher shipping costs related to its one-day shipping program for Prime subscribers.

See More Coverage ›