Police intercepted Mr Puigdemont near the Danish border as the ousted politician attempted to return to Belgium, according to his lawyer, Jaume Alonso-Cuevillas.
Mr Puigdemont “was arrested today at 11:19 am by Schleswig-Holstein’s highway patrol force,” said a German police spokesman.
“He is now in police custody”, added the spokesman.
Mr Puigdemont’s lawyer said on Saturday that the former president had slipped out of Finland. He had been in the country since Thursday for talks with MPs.
A Spanish Supreme Court judge reactivated an international arrest warrant for him on Friday.
Finland’s National Bureau of Investigation (NBI) confirmed on Saturday it had received a European arrest warrant for “a Spanish citizen visiting Finland”. The NBI said they were unaware of the person’s location.
“The president was going to Belgium to put himself, as always, at the disposal of Belgian justice,” said Joan Maria Pique, Mr Puigdemont’s spokesman.