At Google, Mascaraque was head of strategic partnerships and business development for Southern Europe. He will be based with Ask.com in London and will oversee operations throughout Europe.
Jim Safka, chief executive officer, Ask.com, said: "With his extensive online expertise and tremendous business acumen, he will be a great leader for Ask.com's European operations."
Prior to his time at Google, Cesar, a Spanish national, co-founded and acted as director of Finexia.com, a UK-based online asset finance platform.
Cesar said: "With Ask.com as the fastest growing search engine, it's an exciting time to join. I have watched the brand set itself apart from competitors by pioneering new products and offering innovative ways of bringing search to users. I look forward to working with the international teams to build on this already successful model."