In 2016, the company said that it owned more than 59,000 US and international patents and had more than 36,000 patent applications pending.
OIN was founded in 2005 by IBM, Novell, Philips, Red Hat, and Sony and has about 2650 companies as its members. The group acquires patents and then licenses them without any royalty to its members.
The members, in turn, pledge not to use any patents they own against Linux and other open source programs.
"It is no secret that there has been friction in the past between Microsoft and the open source community over the issue of patents," he said.
"For others who have followed our evolution, we hope this announcement will be viewed as the next logical step for a company that is listening to customers and developers and is firmly committed to Linux and other open source programs."
Andersen said the decision to join OIN was an indication of Microsoft’s patent practice going hand in hand with its company’s views on Linux and open source.
The company's former chief executive Steve Ballmer once described Linux as a cancer.
Said Andersen: "We began this journey over two years ago through programs like Azure IP Advantage, which extended Microsoft’s indemnification pledge to open source software powering Azure services.
"We doubled down on this new approach when we stood with Red Hat and others to apply GPLv3 'cure' principles to GPLv2 code, and when we recently joined the LOT Network, an organisation dedicated to addressing patent abuse by companies in the business of assertion."
He said the company would now be be able to do much more to help protect Linux and other important open source projects from patent assertions.
"We bring a valuable and deep portfolio of over 60,000 issued patents to OIN. We also hope that our decision to join will attract many other companies to OIN, making the licence network even stronger for the benefit of the open source community."