Manohar Lal Sharma said Mukesh Singh, Akshay Thakur and Ram Singh should get a fair trial, the BBC reported Tuesday.
Sharma said he would file a representation letter on behalf of his clients Thursday.
"I believe the accused should get a fair trial and I have come forward to represent them," he said.
It wasn't clear how the other two suspects -- Pawan Gupta and Vinay Sharma -- would plead or who would represent them. The lawyers' association in Saket district, where hearings are being held, refuses to defend the accused because of the outcry the crime has provoked.
The five accused were charged with rape, murder and kidnapping Monday. The next hearing is Thursday.
The men are accused of gang raping the woman and assaulting her male companion Dec. 16 on a private bus in New Delhi before throwing the victims from the vehicle. The woman died two weeks later in a Singapore hospital where she was transferred.
The case sent shockwaves of anger across India, leading to demonstrations and a debate about the country's treatment of women.
A sixth suspect will be tried separately in juvenile court if tests confirm he is a minor.
Protesters are calling for tougher rape laws and reforms to the police, who critics say frequently don't file charges against accused attackers.