One-way fares start at €99 ($106) from Europe and $149 from the United States, the company said.
The carrier will operate two A330 aircraft in its own livery, with the aircraft fitted with 293 economy and 21 premium economy seats.
It will operate from Barcelona to the USA cities of Los Angeles and San Francisco, as well as the Argentinean capital Buenos Aires and Punta Cana in the Dominican Republic. A premium economy fare purchase also includes a checked bag, a carry-on bag, in-flight meals, advance seat selection and in-flight movies.
Willie Walsh, IAG chief executive, said Level would become IAG's fifth main airline brand alonside Aer Lingus, British Airways, Iberia and Vueling.
IAG says the A330s will be operated initially by Iberia cockpit and cabin crew.
International Airlines Group (IAG), which operates BA and Iberia, has unveiled plans to launch a new long-haul low-priced carrier.
He noted that Level will share its base of operations with Vueling, allowing passengers to connect from the transatlantic routes to Vueling's continental network. Service is slated to start in June of this year, pending government approval. High speed internet connectivity will be available for a small additional charge.
Level will being flying from Barcelona to L.A. beginning on June 1, with destinations in San Francisco, Buenos Aires and Punta Cana to begin departing in the following weeks.
Norwegian Air, Iceland's Wow air, Canada's WestJet and Morocco's Royal Air Maroc all offer low-budget transatlantic flights for bargain basement prices, to the delight of budget-conscious travelers - and the chagrin of bigger commercial airlines.
"This is just the start", said Walsh.
In a statement, IAG indicated definite plans for expansion to other European destinations in the near future.