"Will decide after a discussion with senior leaders of our party (Karnataka Janata Party) on September 18 and 19," he told reporters soon after the announcement in New Delhi.
Mr Yeddyurappa, BJP's first chief minister in Karnataka, said he welcomed Mr Modi's nomination and he would work for strengthening the NDA (National Democratic Alliance).
The former BJP strongman in Karnataka, who was forced to quit chief minister's post in July 2011 over mining bribery charges, left the party late last year to head KJP. But his party performed poorly in the May 5 Karnataka assembly elections. It won just six seats, including his, in the 225-member assembly.
Since then he has been shifting stands on whether he would return to BJP but has also been saying that he would decide after BJP decides on Mr Modi's role.
A section of Karnataka BJP unit led by former chief DV Sadananda Gowda has been lobbying for taking back Mr Yeddyurappa. H feels without Mr Yeddyurappa's presence the party would not do well in the 2014 Lok Sabha elections in the state.
The BJP had won 19 of the 28 Lok Sabha seats in Karnataka in the 2009 elections.