Soybean and corn prices also fell, pressured by strong export competition and concerns surrounding the immediacy of a US-China trade deal.
Funds piled into net short positions for all three contracts ahead of the weekend.
"The funds are in the driver's seat," said Bill Gentry, a broker at Risk Management Commodities. "They've turned to the short side in corn, beans and wheat."
The most-active wheat contract on the Chicago Board of Trade has lost nearly 9 percent so far this week in what is set to be its biggest weekly decline since July 2014.
On Friday, the May contract was down 12-1/4 cents at $4.47-1/4 a bushel, a new contract low.
Wheat has posted five days of consecutive loses as stiff global competition has fueled worries about demand for US supplies.
Export competition, particularly from South America, has also weighed on soybean and corn futures.
May soybean futures were down 9-1/4 cents at $9.01 a bushel, the lowest level since Dec. 28. The most-active contract was on track to fall about 1 percent for the week.
Corn was set to fall nearly 2.5 percent, the steepest decline since mid-September. The May contract was last down 4-3/4 cents at $3.66 a bushel, the weakest level since Sept. 20.
Brazil's soybean crop forecast was revised upward on Friday, along with the country's second corn crop.
"We've got really powerful export competition moving ahead to the next six months here, assuming that these South American crops are realized," said Brian Basting, an analyst with Advance Trading.
Investors continue to wait for developments in the US-China trade dispute. US President Donald Trump said on Thursday he could walk away from a trade deal with China if it were not good enough, while his economic advisers touted "fantastic" progress toward an agreement.