Niamh Peacock signed for West Ham United women's team on 9 July, penning the first professional contract of her career.

Having spent two years at Chelsea's Academy, Peacock then joined Arsenal at nine years old. She developed through the north London club’s youth set-up and captained their U21s side to the Professional Games Academy U21 PGA Division One title in 2024/25.

Peacock also spent time training with their first team and featured in a senior matchday squad for the first time against Bristol City in the Adobe Women’s FA Cup in January 2025. That was a taste of what was to come, as Peacock spent the first half of the 2025/26 campaign on a dual-registration deal at Watford, where she made 14 appearances to help the Hornets on their way to the FA Women’s National League Southern Premier Division title. In January 2026, Peacock then became the first player to sign an Academy Development Registration contract in the Barclays Women’s Super League 2 when she joined Portsmouth and she went on to make seven league appearances, starting six games, for the south-coast club.