Katy Bourne, who stood as the Conservative candidate in Sussex, was sworn in at a ceremony at the offices of the now-defunct Sussex Police Authority in Brooks Close, Lewes.
Carole Shaves, the vice-chairman of the authority and a serving magistrate, conducted the ceremony by leading Mrs Bourne, from Ansty, through her oath.
Immediately after the ceremony, she began going about her £85,000-a-year role by meeting chief constable Martin Richards.
The police and crime commissioner has the power to hire and fire chief constables. Mrs Bourne will also set police priorities, budgets and the Sussex Police share of council tax.
After her swearing-in, she said: “I am absolutely delighted and extremely honoured to be elected to this position and I look forward to serving the people of Sussex to the best of my ability.
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