The hotel and conference booking agency said the deal, for an undisclosed sum, would boost its overall market share.
Latemeetings.com was launched in 2005 and gives buyers access to 11,000 venues in the UK and Europe.
Expotel CEO Ian Burnley said: "Latemeetings.com delivers the advantages of immediacy, connectivity, 24-7 accessibility, internationality and sustainability. Increasingly, these will be values that corporate and public sector buyers, as well as venue operators, will rate most highly."
He added: "While call centre bookings will continue to dominate, within five years perhaps 25% of all business event transactions will be web-driven."
Expotel is retaining Latemeetings.com directors John Gallery and Chris Martins as consultants.