"There is no basis for speculation that the NCP is joining the government in Delhi," Patel said on Twitter.
The tweet followed reports that his party was likely to join the Narendra Modi-led government and could also get a cabinet berth in the next reshuffle.
The speculation was sparked by a perceived closeness between NCP supremo Sharad Pawar and Prime Minister Narendra Modi.
Pawar, who before the 2014 general elections had said it was difficult to "accept" Modi as the prime minister, now enjoys a good equation with him.
There has been talk of an imminent cabinet expansion, especially in view of vacancies in two key portfolios -- defence and Urban Development.