Lentelli came to America in 1903 and, having already acquired training in sculpture in Italy, was hired by a number of New York sculptors as a studio assistant. Among these were John Massey Rhind, Charles Niehaus, and Adolph A. Weinman. Following his various apprenticeships, Lentelli won a commission to carve a figure of Christ accompanied by a set of sixteen angels for the reredos of the Cathedral of St. John the Divine. For the 1915 Panama-Pacific Exposition in San Francisco, he designed Water Spirit and three Aquatic Nymphs for the Court of Abundance, as well as other works. After the fair, he remained in San Francisco until 1918, teaching at the California School of Fine Arts. A number of sculptures designed as architectural decoration date from this period. Among these were works for the facade of the San Francisco Public Library, mantels for the president's house at Stanford University, and figures for the front of St. Louis's Orpheum Theatre.
On his return to New York in 1918, Lentelli taught at the Art Student's League and the Cooper Union. He established a studio at the famous Tenth Street Studio Building where he lived for many years. Here he designed and executed a number of public commissions including works for the Italian and the International Buildings at Rockefeller Center, an equestrian monument of Robert E. Lee for Charlottesville, Virginia (with Henry M. Shrady), and a memorial to James Cardinal Gibbons (1932) for Washington, D. C. His nude figures, called Golden Sprays, were a feature of the 1939 New York World's Fair. In 1955, the sculptor returned to Rome where he spent the remainder of his life.
He won a number of awards, including several from the Architectural League of New York, of which he was a member. At the National Academy, where he first exhibited his work in 1907, he won the Watrous Gold Medal in 1927 for Sun Dial (cat. no. 100)
