A district called Hamelin was established in 1885 within the PrussianProvince of Hanover. At that time the city of Pyrmont was part of the Principality of Waldeck-Pyrmont. In 1922 Pyrmont decided in a plebiscite to leave Waldeck-Pyrmont and to join Prussia. The Prussian administration assigned the city to the district of Hamelin, which was renamed to Hamelin-Pyrmont.
In 1923 Hamelin became a district-free city and was not part of the district until 1973, when it was reincorporated. Further enlargements of the district's territory took place in 1974 and 1977, when the cities of Bad Münder and Hessisch Oldendorf joined the district.