However, the news and data provider said it expects to see a recovery in the second half of this year as the haltering recovery improves sales.
The firm earned $127m (£84m) in the January-March period, compared with $190m a year earlier.
It said first-quarter underlying profit, which ignores costs associated with the merger between Thomson and Reuters, was $555m, down six per cent from $590m last year.
Overall revenue was static at $3.1bn. Revenue in its professional division was up two per cent to $1.3bn but operating profit fell eight per cent to $289m. The markets division, which depends heavily on long-term subscriptions, reported revenue of $1.8bn, flat year-on-year, but saw operating profits slip four per cent to $323m.
Chief executive Thomas Glocer said: “The tentative recovery in our net sales that we began to see in the second half of 2009 has firmed and accelerated in the first quarter of 2010. We continue to expect that we will see revenue growth return in the second half of this year.
“These improving market trends, coupled with our ongoing investment in new products position us very well for 2011 and beyond.”
Thomson Reuters said it would spend more than $1bn on new technology and products. Among them is Eikon, a new desktop for its financial and trading clients. It also debuted a new version of Westlaw, a large pool of information for lawyers.