In a statement, the company said the move will hit next year's profit by about £15m.
In addition, if the pound averages $1.20 over the financial year, it may lose another £20m.
Overnight on Friday the pound temporarily plunged by 6%, in a flash crash that is thought to have been triggered by automated trading.
Shares in Sports Direct closed down 9% on Friday.
The company had expected to report underlying profit of £300m based on the pound trading at $1.30 against the dollar.
However, the retailer said that "extreme movements overnight" would result "in a negative impact of approximately £15m" on its results for the current financial year.
The swings overnight hit the company's hedging arrangements, which are designed to protect a business against volatile currency prices.
It also sustained a large loss in its last financial year because of currency movements.
In that case, because of a fall in the value of the pound against the euro, it took a £65m hit.
As a result, Sports Direct reported underlying earnings of £381.4m for the year to 24 April against expectations of £420m, resulting in staff missing out on a bonus.
It has been a tumultuous year for Sports Direct which has been criticised for working conditions at its Shirebrook distribution centre. Most recently, its chief executive Dave Forsey stepped down and was replaced by Mike Ashley, the founder and majority shareholder of the retail chain.
The company has an acting finance director after its former financial chief Bob Mellors stepped down in December 2013 after a decade with the business.
Matt Pearson was appointed as interim chief financial officer on 2 June 2015.

Stenson will play with Matt Fitzpatrick against Brandt Snedeker and Brooks Koepka while Rose partners Chris Wood against Jimmy Walker and Zach Johnson.
Rory McIlroy and Thomas Pieters take on Phil Mickelson and Rickie Fowler.
Spanish duo Sergio Garcia and Rafa Cabrera-Bello also stay together to take on Patrick Reed and Jordan Spieth.
Stenson and Rose played together twice on Friday at Hazeltine, and their defeat in the opening foursomes match to Reed and Spieth was their first as a Ryder Cup pairing.
However, they exacted revenge in the fourballs to hand the Americans their first ever loss.
McIlroy, who lost to Mickelson and Fowler in Friday's foursomes when paired with Andy Sullivan, also has the chance to avenge that defeat. The Northern Irishman is again paired with Pieters after they convincingly won their fourball match 3&2.
Europe captain Darren Clarke has also opted to keep Garcia and Cabrera-Bello together after their similarly dominant 3&2 fourball victory on Friday.
American captain Davis Love keeps faith with three of the foursomes pairings that dominated the opening session. The only change is Snedeker and Koepka, who won their fourball match, coming in for Dustin Johnson and Matt Kuchar.
The US won Friday's foursomes 4-0 but Europe hit back in the fourballs, winning that session 3-1.
Sports Direct has warned that the extreme swings in the pound overnight will hit its profits.
[NEXT_CONCEPT]
Henrik Stenson and Justin Rose will partner rookies in Saturday's foursomes as Europe begins day two of the Ryder Cup 5-3 behind the United States.