In 1559 he returned to Poland, where he made the acquaintance of political and religious notables including Jan Tarnowski, Piotr Myszkowski (whom he briefly served as courtier), and members of the influential Radziwiłł family.

Works of his that are pillars of the Polish literary canon [pl] include the 1580 Treny (Laments), a series of nineteen threnodies (elegies) on the death of his daughter Urszula; the 1578 tragedy Odprawa posłów greckich (The Dismissal of the Greek Envoys), inspired by Homer; and Kochanowski's Fraszki (Epigrams), a collection of 294 short poems written during the 1560s and 1570s, published in three volumes in 1584.

[4]: 61  He was born in 1530 at Sycyna, near Radom, Kingdom of Poland, to a Polish szlachta (noble) family of the Korwin coat of arms.

[3]: 186 [4]: 61  It has been suggested that one of his travel companions in that period was Karl von Utenhove [de], a future Flemish scholar and poet.

[9] In mid-1563, Jan entered the service of the Vice Chancellor of the Crown and bishop Piotr Myszkowski, thanks to whom he received the title of royal secretary.

[11] Despite the urging of people close to him, including the Polish nobleman and statesman Jan Zamoyski, he decided not to take an active part in the political life of the court.

Nonetheless, Kochanowski remained socially active on a local level and was a frequent visitor to Sandomierz, the capital of his voivodeship.

[12] On 9 October 1579, the King of Poland and Grand Duke of Lithuania Stefan Batory signed in Vilnius the nomination of Kochanowski as the standard-bearer of Sandomierz.

[18] Kochanowski's earliest known work may be the Polish-language Pieśń o potopie (Song of the Deluge [pl]), possibly composed as early as 1550.

[4]: 62 Some of his works can be seen as journalistic commentaries, before the advent of journalism per see, expressing views of the royal court in the 1560s and 1570s, and aimed at members of parliament (the Sejm) and voters.

[4]: 62–63  This period also saw most of his Fraszki (Epigrams), published in 1584 as a three-volume collection of 294 short poems reminiscent of Giovanni Boccaccio's Decameron.

[3]: 188 [4]: 64  Milosz writes that "Kochanowski's poetic art reached its highest achievements in the Laments": Kochanowski's innovation, "something unique in... world literature... a whole cycle... centered around the main theme", scandalized some contemporaries, as the cycle applied a classic form to a personal sorrow – and that, to an "insignificant" subject, a young child.

It also became one of the poet's more influential works internationally, translated into Russian by Symeon of Polotsk and into Romanian, German, Lithuanian, Czech, and Slovak.

[3]: 188 [23] His Pieśni (Songs [pl]), written over his lifetime and published posthumously in 1586, reflect Italian lyricism and "his attachment to antiquity", in particular to Horace,[4]: 65–66  and have been highly influential for Polish poetry.

[3]: 187 Kochanowski also translated into Polish several ancient classical Greek and Roman works, such as the Phenomena of Aratus and fragments of Homer's Illiad.

[4]: 63  Among works published posthumously, the historical treatise O Czechu i Lechu historyja naganiona [pl] (Woven Story of Czech and Lech) offered the first critical literary analysis of Slavic myths, focusing on the titular origin myth about Lech, Czech, and Rus'.

[3]: 188 From May 2024, the only copy of a work by Jan Kochanowski in the author's hand, the poem Dryas Zamchana, is presented at a permanent exhibition in the Palace of the Commonwealth in Warsaw.

However, he avoided taking sides in the strife between the Catholic Church and the Protestant denominations; he stayed on friendly terms with figures of both Christian currents, and his poetry was viewed as acceptable by both.

[1][2] The Polish literary historian Tadeusz Ulewicz [pl] writes that Kochanowski is generally regarded as the foremost Renaissance poet not only in the Polish-Lithuanian Commonwealth but across all Slavic nations.

[3]: 189  An American Slavicist, Oscar E. Swan [pl], holds that Kochanowski was "the first Slavic author to attain excellence on a European scale".

[26] Similarly Miłosz writes that "until the beginning of the nineteenth century, the most eminent Slavic poet was undoubtedly Jan Kochanowski" and that he "set the pace for the whole subsequent development of Polish poetry".

[4]: 60  The British historian Norman Davies names Kochanowski the second most important figure of the Polish Renaissance, after Copernicus.

[8]: 32  He greatly enriched Polish poetry by naturalizing foreign poetic forms, which he knew how to imbue with a national spirit.

[4]: 63  A number of his works were published posthumously, first in a series of volumes in Kraków in 1584–90, ending with Fragmenta albo pozostałe pisma [pl] (Fragments, or Remaining Writings).