Saarikoski's breakthrough was both critically and commercially Mitä tapahtuu todella? (What is actually going on?) published in 1962. The collection of poems heralded a new era in Finnish culture, laying the foundation of Finnish "participative poetry", a style whose adherents insisted that poets should participate in politics through their work. Indeed, some of the poems featured in the collection do have a clear political tone, whereas in the 1950s Finnish modernists were generally more inclined to think that art should be done solely for art's sake. Mitä tapahtuu todella? marked also a change in the poet's style. His early works Runoja (Poems) and Toisia Runoja (Other Poems), both published in 1958, are not yet "participative poetry" or "democratic poetry" as the poet himself called his style. Instead, they are distinguished by their references to Greek antiquity while the general style was modern, which has led literary critics to say that Saarikoski's first works form his "Greek period". Saarikoski's interest in Greek began very early on. In fact, he studied Greek and literature at the University of Helsinki in the 1950s, though he never received a degree.
During the 1970s Saarikoski continued to publish poem collections. His admiration for the Greek philosopher Heraclitus deepened to such lengths that at one point Saarikoski adopted the philosopher's colloquial name "The Obscure", "Hämärä" in Finnish, to his poetry. Saarikoski began to obscure his poems intentionally and titled one of his collections Hämärän Tanssit (The Dark One's Dances, translated by Anselm Hollo), which is a reference to Heraclitus. While some of his works especially from the late 1960s had received rather morose reception from critics, his last three poem collections which form "Tiarnia-trilogy" (1977, 1980, 1983) are often seen as the second artistic peak point of his career. They were written in Sweden where Saarikoski lived with his last wife Mia Berner. These works reflect pessimism towards technocratic society which is seen as deterring the social participation of citizens. All the works include a word "dance" in their title which refers to a form of social resistance.
Saarikoski also wrote columns by the pen-name "Nenä" ("Nose"). His columns satirized the church, the army, politics and, all in all, conservatism. In his columns, he parodied the official political jargon of his times in a very effective manner.