The first version of the modern Iranian tricolour was adopted in the wake of the Iranian Constitutional Revolution of 1906. The Supplementary Fundamental Laws of 7 October 1907 described the flag as a tricolour of green, white, and red, with a lion and sun emblem in the middle. A decree dated September 4, 1910 specified the exact details of the emblem, including the shape of the lion's tail ("like an italic S") and the position and the size of the lion, the sword, and the sun.
During this period, the colours of the flag were very pale, with the red appearing closer to pink in practice. There were three variants of the flag in use. The state flag was a tricolour with the lion and sun emblem in the centre. The national flag and civil ensign was a plain tricolour with no emblem. The naval ensign and war flag was similar to the state flag, but the emblem was surrounded by a wreath and surmounted by a crown. All three flags had a 1:3 ratio.
The flag was modified twice during the Pahlavi era. In 1933, the colours of the flag were darkened and the design of the emblem was changed. The sun's facial features were removed and the Kiani Crown on the naval ensign was replaced with the Pahlavi Crown. In 1964, the ratio was changed from 1:3 to 4:7 and the emblem on the naval ensign was shrunk to fit entirely within the white stripe.
Following the Iranian Revolution, the Interim Government of Iran removed the crown from the naval ensign. The old state and national flags remained unchanged until 29 July 1980, when the modern Iranian flag was adopted.