The work action could mean as many as 100,000 tourists are turned away from popular sites, such as the Royal Palace in Madrid and the El Escorial Palace just outside the city, thnkSPAIN reported Thursday.
The strikes to protest 15 percent pay cuts and work shifts that run from eight to 20 hours without breaks, thinkSPAIN said.
Work shifts are also scheduled without consultation, thinkSPAIN said.
The strike directly affects 1,200 staff members who work for National Heritage, but staff at other historical sites, including 200 workers at the Zarzuela Palace, are expected to join the strike.
The first-ever strikes against the Crown-owned company are scheduled for Maundy Thursday and Good Friday, two significant days for the tourist industry in Spain.