PillPack delivers prescription drugs to customers' doors.
The deal comes as the health care industry is undergoing a series of convulsions in response to rising costs and pressure on drug makers, pharmacy benefit managers, and insurers.
"We want to help them continue making it easy for people to save time, simplify their lives, and feel healthier".
He added this "is only the first play" in an increasingly aggressive strategy by Amazon for a much more significant role in pharmacy.
"Amazon's acquisition of PillPack is a warning shot in what is about to become a major battle within the pharmacy space", said Neil Saunders, managing director of GlobalData Retail. "We're excited to see what we can do together on behalf of customers over time".
The startup has raised north of $120 million in funding from big-name backers that include TechStars, Menlo Ventures, and Accel.
PillPack, which is aimed at consumers who take multiple medications, presorts customers' prescriptions and helps manage refills and shipping.
It expects to complete the deal in the second half of the year.
Seattle-based Amazon, which began two decades ago as an online bookseller, has mushroomed into one of the world's largest companies.
Amazon is pushing further into pharmacy with a deal to acquire prescription-management service PillPack. Also on Thursday, Amazon announced a new program that will partner with outside entrepreneurs to create a last-mile delivery system for Amazon packages, effectively creating an alternative to UPS or FedEx.
"Over time, Amazon will empower hundreds of new, small business owners to hire tens of thousands of delivery drivers across the USA".