UCLA landed Allen over Washington State and Northwestern. Allen was previously committed to Harvard, but decommitted on Oct. 1 due to financial reasons.
"I am blessed for this opportunity and I will come in and work everyday with something to prove and a chip on my shoulder," Allen said.
Prior to UCLA's involvement, Northwestern was thought to lead for Allen.
He told Chris Emma of PurpleWilcats.com: ""It's close to home, there's the [program's] tradition, and it will be challenging."
Allen joins shooting guards Allerik Freeman and Zach LaVine in UCLA's 2013 recruiting class. Allen had previously committed to Harvard in July, but opened up his recruitment at the beginning of October.