Thomas Ignatius McCarthy was born in Whitwick, Leicestershire on 31 January 1880. His father, Michael McCarthy (1848-1937) had been a publican and this was the occupation he gave in the 1901 England Census, however, not long after this it would seem he became an estate agent and surveyor, and it was in his office, McCarthy & Co. in Coalville, Leicestershire, that Thomas Ignatius McCarthy was articled. In 1906 he purchased his father's firm and commenced practice as an architect.
In c.1911 he formed a partnership, McCarthy, Collins & Co., with Harry Collings (1883-1959) who had previously worked with him as his assistant. Their office was located in Central Chambers, Coalville from 1911 to 1936. McCarthy and Collings remained in partnership until at least 1939.
McCarthy was elected a Licentiate of the Royal Institute of British Architects (LRIBA) in 1911. His address was given as 10 Brooks Lane, Whitwick, Leicestershire in 1891; 227 Talbot Street, Whitwick, Leicestershire in 1901, London Road, Coalville, Leicestershire in 1911; Central Chambers, Coalville, Leicestershire in 1911 and 1914; 1911 and 1936; 16 Meadow Lane, Coalville, Leicestershire and 187 Forest Road, Coalville, Leicestershire in 1939 McCarthy died in Coalville, Leicestershire on 13 February 1951
In 1923 McCarthy, Collins & Co. won a competition to design a War Memorial clock tower for Coalville. The clock was unveiled the following year. Other commissions by McCarthy and by MCarthy & Co. included the Primitive Methodist Church, Marlborough Square, Coalville (1903); Holy Cross Roman Catholic Church in Whitwick, Leicestershire (1904); th Council School in Coalville (1907); a branch of the Nottingham and Nottinghamshire Bank in Beeston, Nottingham (1908); Olympia Picture House, Coalville (1910); the South porch of Saint Andrew's Church, Thringstone, Leicestershire (1911); The Plaza Cinema in Silver Street, Whitwick, Leicestershire (1914); a hosiery factory in Whitwick, Leicestershire (1914); the Working Men's Co-operative Society in Coalville (1915); an extension the the Mowsley Sanatorium in Mowsley, Leicestershire (1918); the TB Isolation Hospital in Hinckley, Leicestershire (1924); the County Sanatorium and Isolation Hospital, in Markfield, Leicestershire (1932); and additions to Our Lady of the Angels Roman Catholic Church, Nuneaton, Warwickshire (1936).
Directory of British Architects 1834-1914. Compiled by Antonia Brodie, et al. Volume 2: L-Z. London; New York: British Architectural Library, Royal Institute of British Architects/Continuum, 2001