It said sales in its FMCG division were down by 12.8% to £20.8m, due to fluctuations in order patterns in its UK commercial channel.
Sales in its retail division declined by 10.9% to £20.6m, following 12 store closures and reduced footfall since Easter.
Despite this, the company said it remained confident in prospects for the current year, and expected to maintain a positive profit growth for the full year, driven by sales.
Jonathan Hart, Thorntons' chief executive, said: “As we said in September, we anticipated that sales for this quarter would be below last year as a result of the increasingly fluctuating order patterns in our UK commercial channel.
“These fluctuations will become more significant within the context of the company’s performance as we continue to grow our FMCG business, making quarterly comparisons less meaningful. As we demonstrated last year, these variances do not necessarily affect overall annual performance.
“We continue to make good progress with our strategy of rebalancing the business and have exciting plans in place for the key Christmas season. We remain mindful that the economic situation is still challenging for many of our shoppers and trade customers, although our growth plans do not depend on an economic upturn.”
At the end of its first quarter, for the 14 weeks up to and including 4 October 2014, the company now has 249 own stores.