Pejačević entered politics as a young man, having become an assessor at the Croatian Parliament seat in Zagreb from 1844 until 1848. As a very influential Croatian politician, he was member of Parliament from the Unionist Party of Croatia and member of the delegation of Parliament that signed the Croatian-Hungarian Agreement in 1868. In 1880 Sabor - the Parliament of Croatia - elected him as Ban of Croatia, and he stayed in office from February 21, 1880, until September 4, 1883.
