Abeokuta Girls' Grammar School was started as a pioneering effort of the Anglican Missionaries, Abeokuta District Church Council (ADCC) that were made up of Anglican Churches and the Stalwart Egba fathers to have a school dedicated to female education in Abeokuta. The first female school was called Anglican Girls' School, a primary institution that was established in 1934 on the premises of St. Peters School , Ake. The School prospered rapidly and was moved to another site at Iberekodo in 1948, where it was upgraded to a Secondary Modern School.

In 1953 three Egba sons Dr. Femi Oyewole, Dr. Dotun Oyewole and Dr. Adeyemi Ademola wrote the memorandum, which brought about the present school. And the Abeokuta District Church Council under the Chairmanship of Late Venerable Archdeacon S.A. Delumo commissioned the school. The ceremony was attended by about 500 guests from far and near. The school started with sharing premises at Iberekodo with the Abeokuta Girls Secondary Modern School before moving to its present permanent site at Onikolobo in 1959. The school was named Anglican Girls Grammar School but it soon metamorphosed into Abeokuta Girls' Grammar School because of the interest of the Egbas in the school. The school started with 2 blocks of four classrooms, one administrative building and one multi-purpose building used for home economics, clothing and textile, and food and nutrition.

On September 21, 1965, Archdeacon R. A. Ashley-Demo, Chairman of the school's Board of Governors, opened the school hostel. The school library-building project started on November 1, 1965 and was opened on February 11, 1966. Between 1966 and 1968, the Chemistry/Physics was officially opened by Oba Adesina Gbadebo II, the Alake of Egbaland. Between 1962 and 1971 the story building of 12 classrooms was constructed and commissioned for use due to increasing number of students.

From 1979 to the early 1980's, the civilian government of Chief Olabisi Onabanjo embarked on progressive educational programs, which benefited AGGS a great deal. During this period, two blocks of three classrooms each and another block for Biology laboratory and introductory Technology workshop were built. From this time, AGGS started experiencing bloated student population, which was not commensurate with the available infrastructures. Thus there has always been the need for more classrooms at the inception of a new academic session. It should be noted that between 1983 and 2004, a period of 21 years, AGGS received little attention from the State government in terms of provision of classrooms. One block of two classrooms each were provided in 1990 and 1998.

In 2004 the present Governor Otunba Gbenga Daniel gave the school a block of four classrooms in honor of Dunni Sobukunola, the AGGS student who had the best WASC result in West Africa in 2002.

The first principal of the school was Ms. L.M. Ouwerkerk, who served from 1955 to 1962. The history of the school would not be complete without a mention of many notable teachers who had effect on the lives of the students that passed through the school. It was the work of the teachers of this period that laid the foundation on which the enviable traditions of the school now rest. Some of the earlier teachers that we remember are; Mama Akinwunmi, E.A Johnson, W. Bajomo. T. Odunlami. C.R Soares, P. Olukoya. T. Prilove, Mr. K Ajayi, Ms. Yetunde Sule, Mr. O. Osinowo, Ms. Fafiolu, Mrs Yejide, Mrs C.O Adeniyi, Mrs G.A Efunkoya, Mrs. P.O Fayemi. Mr. W.S Billings, Ms. G. Billings. Ms. Ruth Martin, Ms. E.A. Maloeni, Mary Eldridge, Mr. Jare Adefemi, Mr. & Mrs. Sharma, Mr. Charles Ehinlaye, Mrs. C.O Egbeyemi, Ms. Fatoyinbo, Mrs . Osfundiya, Mrs. Kayode, Rev. Onimole, Mrs. V.T. Shobo, Ms Mary Kelly, Mrs M.A. Akiniyi, Baba Akande, Chief Ogunfolaji, Baba Edubiyi, Mama G.O. Odukoya, Mrs. Sobukunola, Ms. Akinlawon, Mrs. Toyin Makinde. More teachers equally worth mentioning had passed through the school but it is difficult to name all here.

The school that started with only 30 girls in 1955 today has grown to population of about 3000. Old girls of AGGS make waves all over the world in all fields of endeavors. It is our belief that AGGS will continue to soar higher on the hill, neath the sky of blue, promoting education and values in human kind to the Glory of God