This deal will become effective from July 1.
The 16-year-old Czech Republic youth international striker was named Czech Junior Footballer of the Year in 2005.
Sporting Director Damien Comolli commented: "Tomas has the excellent combination of a strong physical presence, agility and technical ability.
"Two other Premiership clubs were interested in him and we are delighted he has agreed to join us. He is an exciting prospect for the future.Ã¢â‚¬Â
Tomas has already had a number of highlights in his international career. He was a member of the Slavia team that won the Nike Premier Cup in 2004, scoring four goals in the tournament in Helsinki.
Last summer he scored the winning goal against the United States to win the sixth annual Ballymena International Tournament in Northern Ireland and this season he contributed three goals in three games as the Czech Republic qualified for the Elite round of the UEFA Under-17 Championship, which begins at the end of this month.
We are delighted to announce that we have reached agreement for the transfer of Tomas Pekhart from Slavia Prague.