The Moroccan striker was previously with Turkish club Yeni Malatyaspor and the club said further details of the transfer will be revealed on Monday.
But it is believed that the 31-year-old, who was born in France, has signed for a three-and-a-half-year deal for an unknown amount.
Boutaib is a consistent goalscorer and his four strikes in 16 games have put Yeni Malatyaspor in third spot in their League.
He also had a good World Cup in Russia last year, playing in two games with the highlight being his two goals against Spain in a 2-1 draw.
He joins Zamalek at the perfect time as they currently are on top of the League table, eight points ahead of second-placed Pyramids.