Pelosi, a former House speaker, skipped talks in the morning with Italian officials, including the defense minister, as she was taken ill, the ANSA news agency reported.
"After several flights yesterday in Afghanistan, and a long flight back to Italy that arrived early this morning, Leader Pelosi was not feeling well," spokesman Nadeam Elshami said in a statement released in Washington. "This morning in Rome, the leader was advised to visit a clinic, and the closest medical facility was a hospital."
The statement said Pelosi was resuming her schedule in Italy.
The ANSA news agency said the 70-year-old was taken to Rome's Policlinico hospital, where she underwent tests. She was then released and went back to the Rome hotel, ANSA said.
Later Monday, Pelosi held talks with Gianfranco Fini, the speaker of the lower house of Italy's parliament, ANSA said. The talks had originally been planned for earlier in the day.
Pelosi is in Italy with a congressional delegation.