The 20-year-old has struggled to get first-team action at Upton Park this season.
“It feels good to be here. I got a phone call on Sunday night saying that Scunthorpe wanted to take me,” he told the club’s official website.
“As soon as I heard they were interested I wanted to come down and get going really.
“The Championship is a good league to be in, I’m just looking forward to starting my time with Scunthorpe.”
Sears could feature for Scunthorpe against Preston on Tuesday.
“I spoke to the manager on Monday and he said he wants to involve me at Preston, so I don’t know whether I’ll be in the team or not,” he added.
“It will be a quick debut but it will be good to start playing football really.”
