"We arrested him because he is a leader of Hamas, which is a terrorist organisation," said the an Israeli Army spokesman.
Sixty-four other leading figures from the Islamist movement, including eight ministers and 26 mps were detained on June 29.
They were seized as part of a massive Israeli sweep against Hamas following the capture of an Israeli soldier by militants on the border of the Gaza Strip on June 25.
Dweik's wife said that Israeli troops also seized two computers and documents of the Palestinian parliament when they arrested her husband.
Palestinian chief negotiator Saeb Erakat condemned the arrest and demanded the release of Dweik and the other detainees.
Dweik was elected speaker in February following Hamas' victory in Palestinian elections.
He had previously been arrested five times by Israeli authorities, and was also part of a group of 400 Palestinians who were banned by Israel in 1992 and exiled to south Lebanon.
A Palestinian child has killed during a major Israeli incursion in Rafah in the south of the Gaza Strip, Palestinian hospital sources said.
At least 169 Palestinians and one Israeli soldier havebeen killed since Israel launched its offensive in Gaza on June 28.