Additional Sessions Judge J R Aryan held Pehalwan, whose trial had been separated due to his jumping bail and turning an absconder, was also found guilty of destroying evidence. His trial was conducted separately after his arrest in 2005.
The court said it will hear arguments on quantum of sentence for Pehalwan tomorrow.
The court said that Pehalwan was with Vikas and Vishal Yadav during the murder.
Vikas and Vishal were earlier awarded rigorous life imprisonment for their role in the murder of Nitish, a business executive and son of an IAS officer.
According to the prosecution, Pehalwan was present with the convicts Yadavs in their car after they had abducted Nitish from a marriage function at Ghaziabad and killed him on the night of February 16, 2002.
He was chargesheeted in April 2006 for committing the penal offences of murder, abduction and destruction of evidence.
The Yadavs did not approve of the affair of their sister Bharti Yadav with Nitish.