The result of the party's leadership election will be announced today at around 5pm at the Ukip conference in Torquay.
He defeated rival Anne Marie Waters, who had provoked controversy with hostile comments about Islam.
Going forward, Bolton says the party will be focused on unification, gaining back control of British politics and pushing its primary platform.
He said: "Without being united, we can not lead".
He told the party conference: "Brexit is our core task however, it is not the end of the line".
Some Ukip MEPs have said they would quit if Ms Waters won the election.
Outside of Ukip circles, Bolton is a relative unknown.More news: Trump slams mayor of San Juan, Puerto Rico over hurricane relief effort
More news: Trump Administration Waives Shipping Restriction For Puerto Rico
More news: Ryanair extends flight cancellations to early 2018
The emergence of Ms Waters as a candidate in August prompted MEP Mike Hookem to resign his position as party whip in protest, with the MEP stating that he could not "turn a blind eye" to her "extreme views". Bolton reportedly said he was "fine" with the new design.
Mr Bolton said he believes in "old-fashioned, classical liberalism", but feels it has "lost its way a bit".
Under Nuttall the party introduced a so-called "integration agenda" aimed at Muslims, including a proposed ban on wearing a full-face veil in public.
UKIP has held its third leadership contest since the European Union referendum - with a shortlist of seven candidates taking part.
There were a total of 12,915 votes cast in the leadership election, compared with the more than 300,000 secured by Jeremy Corbyn when he was re-elected as Labour leader a year ago.
Bolton stood for the Liberal Democrats in the 2005 general election and has worked for the EU.
The party has been riven by splits and disagreements, one of which resulted in MEP Steven Woolfe being taken to hospital after a fight with another Ukip MEP.
Mr Farage's successor, Diane James, stepped down in October, just 18 days after being elected. The party won no seats and just 1.8% of the national vote, down from the 12.6% of the vote it won in 2015.