Amazon.com is making its biggest acquisition since the 2009 purchase of Zappos.com, agreeing to pay US$775 million ($945 million) for Kiva Systems, a maker of robots that move items around warehouses.
The all-cash deal for closely held Kiva will close in the second quarter, Seattle-based Amazon said.
Kiva's orange robots slide under shelves and bins of products and are used by Quidsi, the parent company of Diapers.com that Amazon acquired for about US$545 million last year.
The takeover of Kiva by Amazon, the largest online retailer, will add to investments chief executive officer Jeff Bezos has made in technology at the company's order centres.
Amazon spent US$4.6 billion on its warehouses last year, the company's largest operating expense at 9.5 per cent of sales and a 58 per cent increase from 2010.