The 991 members of the 36 state Houses of Assembly are elected from single-seat constituencies using first-past-the-post voting; when vacancies occur, by-elections (or bye-elections) are called, scheduled, and administered by the Independent National Electoral Commission.

Candidates' vote share On 26 October 2021, member for Akpabuyo Elizabeth Edem Ironbar (PDP) died from an undisclosed protracted illness.

In the days before the election, observers noted a contentious atmosphere as the two major parties traded accusations of planned manipulation and fears of violence rose.

[15] Candidates' vote share On 26 October 2021, the seat of Ngor Okpala was declared vacant by Speaker Kennedy Ibeh after member Tochi Okere (PDP) did not attend the constitutionally-required amount of legislative meetings.

[22][23][24] On 15 December 2021, the member for Giwa West, Rilwanu Aminu Gadagau (APC), was killed in a bandit attack along the Kaduna-Zaria highway.

[2] Candidates' vote share On 28 November 2021, member for Pankshin South, Henry Longs (APC), died from complications during a leg operation.

"[31] On 29 June 2021, the member for Shinkafi, Muhammad Ahmad (APC), was killed in a bandit attack along the Sheme-Funtua highway in Katsina State.