William Hill said today that trading was hit in the final month of last year due to unfavourable football and horseracing results, meaning the group's profit for 2016 was around £20m lower than expectations.
Shares in the firm were down 3.5 per cent by mid-morning following the announcement.
The bookmaker reported an operating profit of £260m, against expectations of profit between £260m to £280m.
The company said that since its last trading update in November, wagering trends had continued on a similar path, but gross win margins were below expectations.
Group chief executive Philip Bowcock said it was important to note that improvements in wagering in the firm's online and Australia divisions had continued in recent weeks, but added that all four of the company's divisions saw "customer-friendly results at the back end of the year, which translated into profits being circa below our prior expectations".
"With key underlying trends continuing to be positive, the recent run of sporting results have not changed our confidence in a better performance in 2017," he added.
Last year was a tumultuous one for William Hill in a number of ways - in March, the group revealed it had experienced its "worst Cheltenham festival ever" in terms of payouts, but later said the Euro 2016 tournament results had made up for the woeful horseracing experience.
Elsewhere, William Hill rejected two takeover bids - a £3.6bn offer by Rank Group and 888 Holdings, and a subsequent £4.5bn approach from Canadian online gambling group Amaya.