Mike Klis of 9News first reported the news.
With Sanders, the 49ers get a veteran presence for a receiving corps that is largely young and dealing with injuries.
It's an instant boost for the Jimmy Garoppolo-led Niners offense and a sign that John Lynch and the San Francisco front office are all-in and have embraced their status as division frontrunners and contenders for a postseason run.
"Emmanuel is a passionate football player whose toughness and competitive nature have helped him become a dynamic playmaker in this league," Lynch said in a statement. "He possesses a number of qualities, on and off the field, that we value in our players. His familiarity in a similar offensive system will allow for a quick transition. We are excited to add Emmanuel to our roster and look forward to seeing him positively impact our team."
Sanders' run in Denver ends following six seasons in which he made two Pro Bowls and produced three straight 1,000-yard seasons from 2014-2016.
Though he's been dealing with a bit of a knee injury, Sanders has played all seven games this season (and has a chance to play 17 games in the regular season as the 49ers have 10 remaining). He's tallied 30 receptions for 367 yards and two touchdowns -- the TDs would be a team-high on San Francisco and the catches and yards would be first among receivers and second on the team behind tight end George Kittle.
Sanders is coming off an abbreviated 2018 season due to an Achilles tear. As fate would have it, his return to the field came in the preseason against the 49ers. Now with the regular season moving to its mid-point, he's moved on to a contender.
Whether or not, or likely more accurately when, the Broncos would become sellers has been a topic bandied about for Denver GM John Elway and first-year coach Vic Fangio to answer to for weeks. Just a few weeks ago, NFL Network Insider Ian Rapoport reported that anyone other than pass rusher Von Millercould be shipped out. Sanders' name has been one at the top of the rumor mill.
"When we looked at it, Emmanuel had issues and we had issues," Elway said. "That is why it was a good time for us to go different directions, for Emmanuel to go in a different direction and for us to go in a different direction. With that being said, we were able to get the value that we thought was fair. That is why we decided to make the deal."
San Francisco coach Kyle Shanahan was asked Monday about the urgency of bringing in a wideout with fresh legs.
"I mean, I think less than we've had in the last couple of years because I do see that there are guys in our building that I do think the answers are here. It was tough not having Deebo last week, Quise being a little banged up. We'll get both of those two back. The guys we have, I still think can continue to get better. We're still holding out hopes, too, for Jalen and Trent Taylor that they can heal up and hopefully return later this year," Shanahan said. "Always looking to improve, though, like you said, but I do like the guys we have here."