Charles Leonard Hartwell was born in Blackheath, London, England on 1 August 1873 and studied William Silver Frith at the South London Technical School of Art in London, where he won a silver medal, and then at the Royal Academy Schools in London from 1898 to 1903, winning silver and bronze medals. He also received private tuition from Edward Onslow Ford (1852-1901) and William Hamo Thornycroft (1850-1925). He subsequently worked as a sculptor and specialised in figure subjects and portraiture.

Hartwell exhibited every year at the Royal Academy in London from 1905 to 1950. He also exhibited at the Royal Society of Portrait Painters, Royal Institute of Oil Painters and Royal Institute of Painters in Water Colours; Leeds City Art Gallery; Walker Art Gallery in Liverpool; Royal Glasgow Institute of the Fine Arts; West of England Academy in Bristol; and at the Royal Scottish Academy in Edinburgh. He also participated in the exhibition of the Arts & Crafts Exhibition Society in London in 1916.

He was elected an Associate of the Royal Academy (ARA) in 1915; a Royal Academician (RA) in 1924; an Honorary member of the Royal Institute of Painters in Water Colours (RI) in 1918; and a Fellow of Royal Society of British Sculptors in 1923. He was also elected a member of the Art Workers Guild in 1922.

During the 1920s he produced a number of war memorials. Two works by Hartwell were purchased by the Chantrey Bequest: 'A Foul in the Giants' Race and 'Dawn' in 1908 and 1914 respectively.

Hartwell's address was given as 4 Langton Terrace, Woodland's Road, Greenwich London in 1881 and 1891; 8 Manville Road, Upper Tooting, London in 1900 and 1903; 26 Marney Road, Clapham Common, London in 19045 and 1910; The Studio, 62 Acacia Road, London in 1911 and 1934; and Boyne Cottage, Adwick, Bognor Regis, Sussex in 1935 and 1950. He died in Aldwick, Bognor Regis, Sussex on 12 January 1951.