The 61-year-old New Zealander guided the team to World Cup glory on home soil in September last year following a 33-13 victory over Canada in the final at Twickenham.
England have won 25 matches in a row since Mitchell was appointed in 2023, also clinching two Six Nations Grand Slams.
"I am pleased to extend my time with the Red Roses," said the 2025 World Rugby coach of the year, who has previously coached the men's All Blacks.
"This extension provides continuity across a World Cup cycle and enables the programme to operate with a clear, long-term vision."
England return to action on April 11th when they host Ireland on the opening weekend of the 2026 Women's Six Nations.