They opened fire at Jitender Maan Gogi inside the courtroom in Rohini where a case was being heard against him.
Officials say police returned fire, killing the two men. Police suspect a rival gang planned the attack.
Gogi was on Delhi police's most-wanted list and he was also an accused in dozens of cases - including murder, kidnapping and fraud - in other states.
The incident has raised questions over the security of Delhi's courts. A senior politician said that the incident showed a serious lapse in security planning.
