The far-right politician is returning for the first time since supporters stormed the Supreme Court, Congress and presidential palace in January.
The riots came after weeks of protests claiming fraud in his defeat to President to Luiz Inácio Lula da Silva.
Speaking at an airport in Florida before boarding a flight, he said he would not lead the opposition to Lula.
But in an interview with CNN, Mr Bolsonaro also said he would help his Liberal Party as a "person with experience" and that he intended to travel across Brazil to campaign in next year's local elections.
After arriving in the terminal in Orlando, he spoke and took pictures with throngs of supporters.
Mr Bolsonaro is scheduled to land in the Brazilian capital, Brasília, early on Thursday local time (three hours behind GMT).
The former president faces numerous legal challenges on his return, including an investigation into whether he incited rioters who stormed key government buildings a week after Lula's inauguration.