The cabinet of Angela Merkel, the German chancellor, approved the plan on Tuesday prior to the parliamentary vote.
Franz Josef Jung, Germany's defence minister, defended the cabinet proposal in an interview on ARD German public television.
"With the situation in, say, Kunduz [a province in northern Afghanistan] becoming more critical ... an increased number of German soldiers is necessary in the interests of our soldiers' safety," he said.
The reinforcements, demanded by Nato, would also help with the training of Afghan soldiers "so that Afghanistan will itself be capable of assuring its own security".
The decision is not without its critics - Germany's leftist Die Linke party is fundamentally opposed to the deployment of German troops in Afghanistan.
German soldiers in Afghanistan serve as part of Nato's 50,000-strong International Security Assistance Force mission.