The decision was taken by the party's parliamentary board which met in the capital on Sunday.
Mr Modi relinquished the position and proposed Rajnath Singh's name.
Bharatiya Janata Party general secretary Ananth Kumar later told reporters that Rajnath Singh's name was accepted unanimously by all the parliamentary board members.
Party sources said that the decision was expected as Mr Modi could not have run his own campaign.
They said that the sub-committees under the campaign committee were headed by senior leaders and it was expected that Rajnath Singh will be appointed to head the panel.
Mr Modi was declared prime ministerial candidate after protracted discussions in the party on September 13. BJP patriarch LK Advani had not attended the parliamentary board meeting that decided his elevation.
The Gujarat chief minister was declared chief of party's campaign committee for 2014 Lok Sabha polls in June this year.
Source: NDTV