Boris Johnson received almost €60,000 for an appearance in Dublin last month.
Details of the former British foreign minister's payment were disclosed in a parliamentary register of Westminster politicians' financial interests.
Mr Johnson spoke at the Pendulum Summit in Dublin's Convention Centre on January 10th, where he gave a speech and was also interviewed by RTÉ's Bryan Dobson.
In total, the high-profile Brexiteer received £51,250 (€58,350) for his appearance, while transport was also provided.
During the event, Mr Johnson was questioned about his opposition to the Irish backstop and his time in Theresa May's cabinet.
He suggested that "perhaps [I] believed naively that I could make a difference from within Cabinet".
Other speakers at January's summit included the likes of John Cleese and Colin Farrell.
The event, organised by Ireland-based Pendulum Events & Training, describes itself as the "world's leading business and self-empowerment summit".
Mr Johnson is also a former mayor of London.
He resigned from Theresa May's cabinet last July amid political turmoil over her 'Chequers' Brexit proposals.
