The suspect has been identified as Syed Muhammad Kazmi. Reports say he is an Indian national who claims to work for an Iranian publication.
Police said he was expected to appear in court after questioning.
Reports say Indian authorities are investigating whether the suspect had contacts with whoever planted a bomb on the Israeli diplomat’s car.
The February 13 blast wounded the wife of an Israeli diplomat and several other people.
It came the same day as a bomb was defused on an Israeli diplomat’s car in Georgia.
Israel has accused Iran of being behind the plots, a charge Tehran has denied.