The Treaty of Riga was controversial from the very beginning. Many argued that much of what Poland had won during the 1920 war, was lost in the peace negotiations that were by many characterized as short-sighted and petty-minded. They were lacking what brought Poland independence: Józef Piłsudski's combination of far-reaching predictions, and understanding, with his soul and body of a fighter; also, his integrity. In 1921 Piłsudski was no more "The Leader of the State", and was only an observer during the Riga negotiations, which he called an act of cowardice. Due to the disastrous military defeat, Bolsheviks offered the Polish peace delegation substantial territorial concessions in the contested borderland areas. However, to many observers it looked like the Polish side was conducting the Riga talks as if Poland had not won, but lost the war. The exhausted Poles, pressured by the League of Nations, decided to sign the Peace of Riga on March 18, 1921, splitting the disputed territories in Belarus and Ukraine between Poland and Russia. The Ukrainians led by Symon Petliura had been fighting shoulder-to-shoulder with Poles, but in Riga the Soviet negotiators were able to talk Poles into betraying them — to the peril of both Poles and Ukrainians. Those shameless, short-sighted political calculations made Piłsudski deeply ashamed; he walked out of the room, and told the Ukrainians waiting there for the results of the Riga Conference: "Gentlemen, I deeply apologize to you".

The treaty actually violated Poland's military alliance with Ukraine, which had explicitly prohibited a separate peace. It worsened relations between Poland and her Ukrainian minority, who felt Ukraine had been betrayed by her Polish ally, a feeling that would be exploited by Soviet propaganda and result in the growing tensions and eventual violence in the 1930s and 1940s. By the end of 1921, the majority of Ukrainian, Belarusian and White Russian forces had either crossed the Polish border and laid down their arms or had been annihilated by the Soviets.

However, Józef Piłsudski's dream of creating an Eastern Europe alliance (Międzymorze) of independent countries was thwarted by this treaty, as Poland was unable to fulfill the obligations of its alliance with Ukraine and support its independence, and Polish-Lithuanian relations deteriorated as well as a result of Poland's annexation of the city of Vilnius, which the Lithuanians claimed as their capital.

On the other hand, the Treaty of Riga led to the stabilization of the eastern border of Poland. The new Polish state surrendered most of land lost in 1st and 2nd partition to Russia by the Polish-Lithuanian Commonwealth during partitions of Poland, with a sizeable Polish minority (less than 1 million) especially around Słuck and Żytomierz. This would allow Soviets to carry out harsh reprisals against those Poles - begun with confiscation immense property (land, forests), persecution of religion (bishop Cieplak 1923) and eventually full scale deportation of Poles to Kazakhstan 1931-1934. Population living on the Polish side of the Riga border, including Poles and (approx. 6 million citizens) minorities of Ukrainians, Belarusians, Lithuanians and Jews were protected from totalitarian dictatorship, and guaranteed freedom of property and religious faith - for the next 18 years. However, this didn't protect them from ethnic conflicts, especially during the Great Depression from 1929 on.

Poland also was to receive monetary compensation (30 million rubles) for its economic input into the Russian Empire during the times of partitions of Poland. Russians were also to surrender arts and other Polish national treasures pillaged after 1772. Both sides renounced claims to war compensation.