The agency, which pitched against Mustoe Merriman Levy, Fallon and Heresy, will be working to reverse a 3.5 per cent fall in sales in the past year and attract more female readers.
The paper's managing director, Sally de la Bedoyere, will raise its above-the-line spend to £4 million as it gears up for a series of product development initiatives. Partners' advertising will also support promotional activities.
The Partners chief executive, Nigel Long, said: "It's about finding a creative vehicle which accurately captures the voice of London. The Evening Standard is a strong brand in the capital, but it could be stronger. The win replaces the gap left when Partners lost The Guardian account last year.
Long added that the agency would work closely with its new editor, Veronica Wadley, who replaced Max Hastings at the beginning of the year, to ensure any campaigns were allied with its editorial.
The most recent ABC figures revealed the 3.5 drop in sales and reinforced the paper's need to refocus on 18- to 34-year-old women.
Wadley has already made changes to the paper's editorial, replacing staff and revamping its arts coverage. The Standard made its marketing director, Jane Hayman, redundant in February and has not replaced her.
Bates UK previously handled the account, and created the Standard's last major campaign last September.