The men are suspects in a December 2012 robbery which saw booty worth €23 million ($31 million) stolen from a luxury watch store in Madrid.
More than 1,700 watches were nabbed during the crash-and-bash style raid.
Police have now recovered 300 of the stolen timepieces, worth some €270,000, Spain's La Vanguardia newspaper reported on Thursday.
Spanish authorities, working with Interpol, have also located more of the stolen watches in Shanghai where they are being traded on the black market.
Police have detained a total of 17 suspects in the case, including the actual thieves, middlemen, and others received of stolen merchandise.
One of the man arrested — "The troll" — is a well-known thief with a history of robberies on Madrid's so-called 'Mile of Gold'. He is considered the chief suspect, police say.
Police searches have also turned up weapons, drugs, jewels, and tools used in robberies such as oxy-fuel cutters.