The sports retailer said on Thursday that its pre-tax profits plunged to £77.5 million in the year to April 29, from £281.6 million a year earlier.
It was impacted in part by an investment in Debenhams, having increased its total stake to 29.7 per cent during the period.
The company upped its holding in the struggling department store chain in March, bringing it close to a level at which it must launch a takeover bid.
But a recent reduction in Debenhams’ value meant Sports Direct took an £85.4 million hit as a result - having been offset in part by investment income.
The total loss on that investment was otherwise £98.1 million.
The company also has strategic investments in businesses including Goals Soccer Centres, French Connection, and House of Fraser.
Shares in Sports Direct dropped as much 11 per cent in early trading.
Sports Direct said comparative figures from a year earlier were tough to match, having been boosted due to its sale of JD Sports shares and the disposal of the Dunlop brand.
The loss of Dunlop also hit revenues from its wholesale and licensing division, which dropped 22.7 per cent to £186.3 million, but the disposal eased operating cost pressures which decreased by 31 per cent.
Total group revenue for the period was up 3.5 per cent at £3.4 billion, though its UK sports retail sales fell 2 per cent to £2.2 billion.
But founder Mike Ashley tried to turn attention to the group’s underlying profits.
“I’m pleased that our underlying EBITDA has come in at the top end of our expected range at £306.1 million as we indicated this time last year, and also that the underlying profit after tax has increased substantially to £104.9 million,” he said.
Sports Direct is likely to benefit in the next financial year from the sale of its remaining stake in JD Sports, after the sportswear rival completed its takeover of The Finish Line.
It helped Mr Ashley’s business net £45.2 million in proceeds.
Commenting on the full-year results, analysts led by Liberum’s Adam Tomlinson said it was a “strong outcome”, having been nearly 23 per cent ahead of their own forecasts.
“When one considers the heavy lifting as the strategic shift to the elevated store and online offering continues and the retail backdrop during the year, this is a commendable achievement with revenues marginally higher.
“Tight control on costs and benefits from infrastructure investment and automation has started to deliver efficiencies in the UK and Europe,” they added.
“A strengthened senior team, a focused and disciplined strategy that places property and brands at the very centre should result in increased customer loyalty, frequency of visit as as merchandising, availability and product lines improve over the next few years.”