"The (German) federal government does not recognise such an independence declaration," spokesman Steffen Seibert said in a statement posted on Twitter.
"The sovereignty and territorial integrity of Spain are and always will be inviolable," he added.
"We hope that those involved will use all available opportunities for dialogue and de-escalation."
The political crisis in Spain escalated sharply after Catalan lawmakers voted to declare independence and Madrid in turn vowed to "restore legality" and quash the region's secessionist bid.
Seibert's comments echoed those of EU President Donald Tusk who called for calm and said that Madrid remained the bloc's "only interlocutor".
The European Union and its member states have stood firmly behind Madrid in the standoff triggered by Catalonia's hotly contested October 1 referendum on splitting from Spain.
Seibert said the German government was following the latest developments "with concern".