The Shin Bet said the operatives were working to enlarge Hamas' infrastructure in the territory and establish areas where they could yield influence, such as charity work and education.
The agency said the Hamas operation was partly financed by gold smuggled into the West Bank from neighboring Jordan.
Hamas has ruled the Gaza Strip with an iron fist since ousting forces loyal to the rival Palestinian Fatah party led by President Mahmoud Abbas in 2007, leaving him governing parts of the West Bank.