But she added that she would try to prevent job losses that may be caused by the move.
"The Social Democrats (SPD) will not conclude negotiations without a universal legal minimum wage," Merkel said, as the coalition talks between the SPD and her Christian Democratic Union (CDU) and its Bavarian sister party the Christian Social Union (CSU) entered the final phase.
Merkel: Will try to prevent job losses that may be caused by the move
Negotiators from the two sides have been trying to hammer out a detailed programme of policies and reach agreements on key cabinet posts of the "grand coalition" to rule Europe's largest economy for the next four years.
The new government is expected to emerge by Christmas.
The introduction of a national minimum wage of 8.50 euros (about $11) per hour is a key election platform of the SPD.
Merkel's party opposes national minimum wage but supports minimum wage deals struck by employers and trade unions in different industry sectors and regions.
She has reiterated her opposition to the national minimum wage on concerns that it would destroy jobs.
Germany's leading economic institutes warned in a report last month that the introduction of a minimum wage of 8.50 euros per hour could lead to significant job losses in eastern Germany.
The report showed that 11 percent of workers in western Germany earning less than the proposed 8.5 euros an hour, while in eastern Germany a quarter of workers are earning less than the amount.