The AfD won the Mecklenburg-West Pomerania state election with 37%, slightly ahead of the SPD on 35.5%, according to an ARD exit poll.
However, the SPD of the country's incumbent Prime Minister Manuela Schwasig is expected to get enough support to build a coalition and oust the AfD from the government. Schwesig was the leading candidate of the SPD in the elections.
Chancellor Friedrich March's CDU collapsed to just 5.5% - its worst result in any German regional or national election since World War II.