Derwent Smithurst was elected to the vacant seat by 280 votes, defeating challenger Frederick George Fisher III, who received 185 votes.
The by-election was held on 18 February.
Mr Smithurst will serve as an Alderney States member until 31 December 2026.
470 votes were cast representing a 35% turnout of the island electoral roll. Five voting papers were spoilt.
It was the first election in Alderney where 16- and 17-year-old’s were eligible to vote.
Election day in Alderney!
Good turn out so far. Both candidates have been working hard over the last few weeks.
Best of luck to Frederick George Fisher III and Derwent Smithurst.
Thank you for ensuring an election takes place for a member of @States_Alderney pic.twitter.com/7Bv73x2kLz
— Alex Snowdon (@AlexSnowdon5) February 18, 2023
The by-election was scheduled after the previous election only saw four candidates nominated for five seats meaning they were elected uncontested.
Alderney elects half its government every two years.
The plebiscite in December to elect two representatives for Alderney in the States of Guernsey was contested with three men vying for the two seats. Steve Roberts and Alex Snowdon ultimately retained their positions.
