Kurdish and nationalist deputies nearly came to blows during a tense debate over a reform aimed at breaking a deadlock in trials of hundreds of people accused of links to the Kurdistan Workers' Party (PKK) militant group.
Courts have rejected suspects' efforts to use Kurdish in defending against charges of membership in a PKK umbrella group. The new law will allow defendants to speak in their mother tongue, if they speak it better than they do Turkish.
The court defence reform was among the demands of hundreds of jailed PKK rebels who late last year staged a hunger strike which was ended by the intervention of their leader Abdullah Ocalan, in prison on the island of Imrali.
Mr Ocalan's intervention is viewed as having paved the way for the government to launch peace talks.
Intelligence agency officials have held talks with Mr Ocalan, establishing a framework for a deal under which the PKK would stop fighting, withdraw from Turkish soil and disarm, according to media reports.
In return, the government would carry out reforms boosting Kurdish minority rights.