"He has made history, he is the first Muslim mayor of a big European city," Hidalgo told reporters on the platform after Khan welcomed her off the cross-Channel Eurostar train from France.
Describing him as a "progressive" and a democrat, she said his election "is an example for us", before they left to discuss their shared challenges of pollution and affordable housing at a cafe nearby.
Khan, a member of Britain's opposition Labour party, was elected mayor on Thursday with 1.3 million votes, the largest personal mandate of any British politician.
He responded to Hidalgo's warm words by pointing out that she too had "made history, she was the first woman ever elected mayor of Paris" when she took office in 2014.
Khan said they both had similar values and history, while Hidalgo noted: