Operating profits at the group's British radio arm were down 63% to £2.5 million with revenues also hit by an unfavourable year-on-year comparison with a period including the Euro 2012 tournament.
TalkSport, which recently lured presenter Colin Murray from BBC's 5 Live, will be hoping an expected economic recovery can help bolster its fortunes for the remainder of 2013.
A £3.4 million fall in advertising at the station contributed to a 14% decline in UTV's British radio division revenues, which also includes local broadcasters.
Pre-tax profits at the wider group, which includes a TV business in Ireland, fell 43% to £6.1 million. Shares were down 4%.
July advertising revenues in British radio continued the downward trend but talkSport expects to see improvements of 5% in August and 10% in September.
The build-up of interest in next year's World Cup, with the draw taking place at the end of this year, should provide further opportunities, it added.
UTV chairman Richard Huntingford said the year might be described as a "game of two halves" as a slow start gives way to better performance later in the year.
"In particular, talkSport's revenue, which was impacted in the first six months by poor market conditions and the absence of a major sporting event, is forecast to grow in the post summer months, contributing to an overall improvement in GB Radio's performance," he said.
Mr Huntingford added that signs that the broader economy was finally picking up suggested better times ahead.
He said: "Recent macroeconomic data suggests that we are heading towards recovery which should see advertising enjoy renewed growth."
The group's interim results for the first six months of the year covered a period when it renewed Premier League broadcasting rights for the next three seasons and achieved its highest ever audience.
It also extended its rights to broadcast top-flight commentary across Europe - now available in nine languages. Further deals have now been signed for markets in China, Malaysia, Vietnam and the US.
Television advertising revenue in Ireland fell over the six months though was expected to grow in the third quarter.