As a national school, it is controlled by the central government, as opposed to a Provincial Council. The school has more than 5,500 students on a campus spread over 10 acres (40,000 m2). The academic staff consists of more than 200 people. The institution was founded in 1954 by W.A.K. Gunawardana in Sri Wardanarama, Colombo, with just five students in the class. In 1958, the school was registered
as a government-assisted junior school. The number of students gradually increased to 163 with four staff members and, on January 1, 1960, J.D.A. Jayakodi was appointed as the first principal of the school. By 1969, there were 14 staff members and 373 students. With the rapid increase in student enrollment, the school moved to a nearby location, Valukarama. Primary classes were held in a nearby building, Thurstan College. In 1974, during T. Silva's time as principal, the junior school at Thurstan College moved to its present location, Mahanama College. In 1975, 130 students sat for the N.G.C.E. examination, and 107 students passed the exam. The government donated 7 acres (28,000 m2) of land as the school expanded. By 1976, the site contained several two-story buildings. During the early 1970s, principle N.E. Fernando, made improvements to the school's facilities, including the construction of a dental unit and additional classrooms, as well as the first two-story building. Principal K.N.P. de Silva retired on 5 February 1986, and was succeeded by D.G. Sumanasekera. Sumanasekera was the first SLEAS Class-1 principal to head Mahanama. During his four years in office, he laid the foundation for the present school. K.K. Rathnadasa became principal in 1990 and, during his time at the college, several three-story buildings were constructed, a computer section was established, and a children's park was created. The annual carnival 'Foot-Loose' was also organized during his tenure. In 1999, G. Liyanage became principal. He added a three-story building with an art gallery to the existing campus. During his tenure, the school laboratories and computer sections were improved and buildings renovated. The Battle of the Golds, the so-called "Big Match" between Mahanama College and its friendly rival D. S. Senanayake College, Colombo, was inaugurated. Rev. Vahalle Dhammananda (1954–1960)
J.D.A. Jayakody (1960–1968)
N.E. Fernando (1968–1974)
T.S. Silva (1974–1976)
K.N. P. de Silva (1976–1986)
D.G. Sumanasekara (1986–1990)
K.K. Ratnadasa (1990–1999)
G. Liyanage (1999–2003)
W.H. Pramalal Kumarasiri (2003–2012)
U.M. Prasanna Upashantha (2013–2016)
L.M.D.Darmasena (2017-2020)
A.C.Perera (2021-Present)
