The two thieves struck a truck parked outside a wholesale centre in Gävle on Sweden's east coast on Tuesday morning, but a security guard noticed the pair mid-heist and gave chase.
The thieves dumped their stolen treats during the getaway, but the guard managed to catch one of them, an 18-year-old man, while his accomplice escaped.
"As I understand it, all the ice cream was still (in the bags). And a lot of it had melted so it had to be thrown away," Mikael Hedström, spokesman for the Gävle police, told the Aftonbladet newspaper.
"This is one of the most unusual crimes I've been involved in."
The 18-year-old has been detained on the suspicion of theft, while the police are still on the hunt for his accomplice.