Leo, 71, was treated at Rome's Gemelli hospital for the removal of the small nodule, which the pontiff said on Sunday had been spotted early during a recent check-up.
"The procedure was completed successfully, within the expected timeframe and as planned," said a brief Vatican statement issued late on Tuesday that did not offer further details.
The Vatican said earlier that the procedure was led by the Gemelli's chief thoracic surgeon Stefano Margaritora.
Leo left the Vatican ahead of the surgery shortly before 1pm in Rome and was seen waving from the back of a black SUV as his convoy drove about 9km north of the Vatican to the Gemelli.
Upon arrival at the hospital, Leo shook hands with several officials, walked in front of a waiting crowd of well-wishers, some of whom shouted "Auguri" (best wishes), and headed in via the main entrance.
Tuesday's surgery should help determine if the growth is malignant or what further treatment is needed, according to medical experts.
The Vatican did not say what tests had been performed on the nodule in its evening statement.
The Vatican has said the Pope is expected to recover in hospital for about a week.
All his public events have been cancelled until October 20.
Leo, elected by the world's cardinals in May 2025, is relatively young for a Church leader.
He enjoys sports, including tennis, and is not known to be a smoker or to have had recent health issues.
A nodule on the lung is a small, localised lesion that can be benign.
The American Thoracic Society says fewer than five per cent of lung nodules overall prove cancerous although risk rises with age, size and other factors such as smoking.
Federico Venuto, chief of thoracic surgery at Rome's Policlinico Umberto I Hospital, said procedures to remove lung nodules were usually minimally invasive and can sometimes involve the use of a thin camera tube called a thoracoscope.
"The complication rate is extremely low," he told Reuters.
Leo, who spoke in a firm, clear voice at his only public event on Monday, keeps a very busy schedule.
He is due to make an 11-day tour of Uruguay, Argentina and Peru from November 6 to 17.
Having the surgery promptly gives him the best chance to keep his South American trip on schedule.
The suite in Gemelli where pontiffs usually stay during treatment is currently unavailable because it is being renovated.
The Pope is the ultimate earthly authority for the world's 1.4 billion Catholics and does not have a deputy who steps in when he is sick.
When a pontiff is incapacitated the business of the Vatican's vast bureaucracy carries on as usual, holding off on any decisions that require papal approval.
Leo, born in Chicago in 1955 as Robert Prevost, served for decades as a missionary and bishop in Peru.
In 1985, when he was a young priest, he came down with typhoid fever in Chulucanas, Peru and was hospitalised.
He recounted the experience in his only major interview given as pontiff, in a book for Penguin Peru.
Leo said the pain was so bad that he asked God to die rather than continue suffering.
He took his survival as a sign from God that "We need you here (on Earth)," he said.
"I never looked back," Leo said.
