The vote came after an emotional debate in parliament, as the issue is still sensitive in a country where the Nazis deployed what it called "euthanasia" to exterminate around 200,000 disabled people.
Under the new law, passed with 360 in favour out of 602 votes, assisted suicide remains permitted in Germany, but anyone who turns it into a professional service -- with or without payment -- faces three years in jail.
In practice, this means that a husband who helps his terminally ill wife to die would not be prosecuted.
But an association or a business that repeatedly offered to help people die would face prosecution.
The situation is not so clear-cut for doctors who prescribe deadly cocktails to patients.
Critic Renate Kuenast, from the opposition Greens, warned that "banning the professionalisation of assisted suicide puts doctors in danger of prosecution".
But Michael Brand, a Christian Democrat lawmaker who co-authored the bill put to parliament, argued that the intention is not to punish doctors but to ensure that patients are not coerced to die.
"Our draft law does not seek to criminalise doctors... it is aimed at protecting people from dangerous pressures," he said.
In 2012, a German assisted-suicide organisation, StHD, pre-empted the new legislation by moving to Switzerland, saying then that it feared prosecution if the German legislation passed.
According to a survey published at the end of October by Focus weekly, 74 percent of those surveyed supported suicide assisted by a doctor, while roughly 20 percent were opposed.