The arrest took place on Wednesday afternoon, however the stolen jewels have not been recovered and the search is continuing.
A decision will be made by midday on Saturday as to whether the suspect will be kept in police custody.
The search for both the culprits and the jewels gained international attention after 17th-century royal crowns were taken from a cathedral in Strängnäs, one hour from Stockholm, where they had been kept in a locked and alarmed display case.
The suspects were seen fleeing from the scene on women's bicycles and then a motorboat, and police carried out searches by water and air.
A police spokesperson told told The Local in early August that the forensic team had found “traces” both in and outside the church, but said it was too early to say what kind of evidence these might be.
The crowns were made for the burial of Kind Charles IX and his wife Christina, and date back to the early 1600s. A royal orb was stolen along with them, and the gold jewels are decorated with silver and pearls.
July's royal heist was the second to take place in the area around Lake Mälaren in recent years.
In 2013, a crown and sceptre used in the funeral of Sweden's King Johan III were stolen from nearby Västerås. Those items were later located in two large rubbish bags at the side of a highway following a tip-off to police.