He fled from Spain in October following an illegal declaration of independence by the region.
Puigdemont had recently left Finland before authorities there could act on a European warrant against him.
Police did not say exactly where Puigdemont, who had been living in Brussels since late October, was being held but the Spanish press said he was at a police station in the nearby town of Schuby.
Puigdemont himself had said from Belgium in early March that he was abandoning his bid to return as regional president, even though he had run in December's polls from overseas.
This past week, a Spanish Supreme Court judge, Pablo Llarena, issued global arrest warrants for six Catalan politicians, including Mr. Puigdemont, and ordered five other Catalan politicians to be detained without bail.
According to the lawyer, the German police are now carrying out all the necessary checks within the framework of the European arrest warrant.
The Spanish prosecutor's office said on Sunday it was working closely with counterparts in Germany and EU agency Eurojust to provide all of the information needed to make the European arrest warrant for Puigdemont effective.
Carles Puigdemont said that he was ready for talks with the Spanish central government, and believed that his return would be evidence of the normalization of politics and democracy in the country.
The ex-leader is being sought by Spanish authorities on charges of rebellion, after he led his separatist movement in a bid for an independent Catalonia. He faces a 30-year prison sentence if convicted.
Germany now has 60 days to determine whether to extradite Puigdemont to Spain.
On Friday the Spanish government reactivated an worldwide arrest warrant for Puigdemont, who is wanted on charges of sedition, rebellion and misuse of public funds.
Puigdemont was crossing from Denmarkon the way to Belgium when he was detained by a highway patrol Sunday morning in the northern state of Schleswig-Holstein, German police said.
13 other separatist politicians were charged with similar offences in Spain last week.
The detention of the fugitive ex-leader of secession-minded Catalonia has sparked mixed reactions in Spain.
Thousands answered the call by a pro-independence grassroots group to protest in the city center hours after Puigdemont was detained by German police.
Puigdemont's spokesperson, Joan Maria Pique, told Reuters the former Catalan leader was on his way back to Belgium before he was arrested in Germany. She had moved to Scotland from Belgium earlier this month.
F1 sees distinguished manufacturers make a welcome return
It would also be nice to see a more competitive side to the sport, which usually sees one side dominate the entire season. The team is looking at Charles Leclerc from Ferrari, Marcus Ericsson or Antonio Giovinazzi who is a reserve for Ferrari.
Cyber Monday 2017 – The top sellers in electronics this year
Apple’s 9.7-inch Wi-Fi enabled iPad Pro was also still a great seller thanks to massive price discounts from retailers. Microsoft dropped their game changing console update, the Microsoft Xbox One X with a 1TB hard drive and 4K compatibility.