Act No. 136 dated June 11, 1901, which became effective on June 6, 1901, created the position now occupied by the Solicitor General. Under Section 40 of this Act, the Attorney General, as head of the Bureau of Justice, was vested with the powers and functions of today's Solicitor General. At the time, the Solicitor General was second only to the Attorney General in the office the former would eventually head. Appropriately, Section 41 of the Act required an "officer learned in the law" to assist the Attorney General. This law specifically provided that "it should be the special duty of the Solicitor General to conduct and argue suits and appeals in the Supreme Court, in which the Philippine Government is interested."
Meanwhile, a few months after the Bureau of Justice was created, Act No. 222 was passed, establishing the Department of Finance and Justice. The Bureau of Justice was placed under the supervision of a new department. Act No. 2666 would later divide the department into a Department of Justice and a Department of Finance. Under this law, the Attorney General and Solicitor General continued to represent the Government in the Supreme Court and lower courts.
Act No. 4007 which was enacted in 1932 abolished the position of Attorney General. His functions were taken over by the Secretary of Justice. The Act also named the Solicitor General as the head of the Bureau of Justice. The Assistant Solicitor General, a position created by Act No. 683 of 1903, became second in command of the Bureau.
As a result of the rapidly burgeoning number of cases involving the Government, the Solicitor General after independence was constrained to concentrate on advocacy and court appearances. The functions which the Bureau of Justice used to have were gradually transferred to newly-created offices and divisions of the Department of Justice.
Executive Order No. 94 of 1947 renamed the Bureau of Justice as the Office of the Solicitor General. Subsequently, the legislature passed R. A. No. 335 in 1948 to confirm this change and to provide for a First Assistant Solicitor General who would be the second highest official in the Office.
A succession of laws relieved the Office of the Solicitor General of some of its burdens. Section 1660 of the old Administrative Code previously provided that the head of the Bureau of Justice "shall have general supervision and control over provincial and city fiscals (now prosecutors) and attorneys and over other prosecuting officer throughout the Philippines." The Office of Special Prosecutors, which the Solicitor General formerly headed, was later converted into a Division of Special Attorneys by R.A. No. 311 of 1948. The Office of the Government Corporate Counsel, which was headed by the Solicitor General under Executive Order No. 392 of 1950, became a separate office in the Department of Justice by virtue of R.A. No. 2327.
From a motley staff of one Solicitor General, an Assistant Solicitor General and a handful of assistant attorneys in the 1900's, the Office of the Solicitor General has grown throughout the years. In accordance with E.O No. 292, the Administrative Code of 1987, the Solicitor General was assisted by fifteen Assistant Solicitors General and more than a hundred Solicitors and Associate Solicitors, who are divided into fifteen divisions. In 2006, with the passing of Republic Act 9417 or the OSG Law, the Office has expanded to thirty (30) legal divisions with a corresponding increase in the general and administrative support personnel and provision for ample office space.