Protheroe will be responsible for overseeing production and excellence in client service at Pollen.
She joins from Stream Digital Media, a division of Ascent Media, where she led the development of digital services and headed up production and client services.
Protheroe was previously at marketing and communications agency DeepSync, advising football clubs such as Manchester United and Liverpool.
Dan Dimmock, director of strategic development at Pollen, said: "Lucy is an utter professional. Her experience will act as a catalyst for the seamless evolution of our client campaigns and the consistent high standard of production in Pollen's output."
Pollen's clients include , BSkyB, VWater (Pepsico International), Renew, Havas' MPG and E! Entertainment.
Protheroe said: "I'm joining Pollen at an exciting stage. The business is growing and I will be acting as a brand guardian for Pollen's reputation of producing consistent and intelligent creative execution."
Earlier this year, Pollen appointed Peter Stimpson, former Enterprise IG (The Brand Union) creative director, as a senior branding adviser.