The bookmaker, which operates about 2,300 betting shops across the UK and Ireland, says marketing outlay hit £28.3m in the six months to 30 June.
The firm, which operates gaming and sports betting website William Hill Online, has launched a number of campaigns in recent months including a scratchcard promotion at the end of the last football season and an outdoor campaign to push the website.
The bookmaker also recently replaced BetNOW as the partner of The Sun’s Dream Team 2009/10.
News of the uplift in advertising spend comes as the company reported a 9% dip in operating profit to £131.8m, hit by quieter trading at weekends after the football season ended in May.
Yesterday (4 August) announced it was moving its online betting service, Sportsbook, and online fixed-odds games from the UK to Gibraltar to cut costs.