14 October 1912 is regarded as the date when Riga Zoological Garden was officially founded. On this day an official document of acceptance was signed. The Society "Zoological Garden in Riga" had established a modern zoological garden. Financial support was provided by donations.

The Zoo's development was stalled by World War I. In August 1917 the Zoo was closed. A part of animal collection was moved to Germany, another part was sold, the rest of animals had to be put down.

In 1921 the territory of the Zoo was handed to the Department of Social Security, and summer camps for children of low income families were established at the site.

On 24 September 1933 the Zoo reopened in a part of its former territory. The new society, "The Latvian Zoological Garden", managed the restoration of the old exhibits and the building of new ones. The Zoo started to prosper again. By 1940, the Zoo had recovered all its original territory.

Riga Zoological Garden remained open throughout World War II. At the end of the war, the Zoo's staff managed to save the animal collection from moving to Germany again.
During Soviet times, the Zoo developed a rich animal collection despite restrictions characteristic of that time period. Riga Zoological Garden was considered one of the best zoos in the Soviet Union.

When Latvia regained its independence in 1991, the Zoo was in a shabby shape, with neglected buildings and infrastructure. With the help of financial support from the government, the municipality of Riga and sponsors, the Zoo's dedicated and creative staff managed to improve and develop the Zoo.

In November 1992, Riga Zoo joined the European Association of Zoos and Aquaria (EAZA). In December 1992 the Supreme Council of the Republic of Latvia approved the Zoo's renaming to Riga National Zoological Garden.