The financial terms of the deal have not been disclosed. Amazon confirmed the deal to Bloomberg.
Shares of Amazon were off 0.27% to $3,268.95 in trading on Tuesday.
"We have signed an agreement to be acquired by Amazon and are looking forward to working with them as we continue to build easy-to-use tools for entrepreneurs," wrote Selz Chief Executive Martin Rushe in the blog post.
Selz is a seven-year-old technology provider that helps small businesses operate e-commerce sites and process payments. It has received total funding of $11 million, according to Crunchbase, and has offices in Sydney, Australia and Manila, the Philippines.
"Nothing is changing for our customers at this time, and we'll be in touch with customers as and when we have further updates," Rushe added.
Selz competes with the likes of e-commerce software provider Shopify (SHOP) - Get Report, which is popular among many online sellers because the Canadian company gives them more control over the customer experience, Bloomberg reported.
Earlier this month, Amazon said that founder and CEO Jeff Bezos will step down and become executive chairman, marking the biggest change in leadership of the tech giant in 26 years.
Andy Jassy, who currently heads up Amazon Web Services and will become Amazon's next CEO, has reportedly affirmed his commitment to making video games, while acknowledging the difficulties his team has encountered.
Jassy will succeed Bezos in the third quarter this year.