[1] Osiecka was born in Warsaw, the only child of Wiktor Osiecki, a pianist and composer of Serbian, Romanian-Vlach and Hungarian descent, and a scholar Maria Sztechman.

Renown Polish actress Kalina Jędrusik sang Osiecka's lyrics to a hit song by Franciszka Leszczyńska called "My First Ball" (Mój pierwszy bal).

One year later at the first National Festival of Polish Song in Opole in 1963 Agnieszka achieved a major success winning the main prize and six other prizes for her lyrics: "Piosenka o Okularnikach“ (music by Jarosław Abram), as well as "Białe małżeństwo,“ "Czerwony kapturek,“ "Kochankowie z ulicy Kamiennej,“ "Solo na kontrabasie“ and "Ulice wielkich miast.“[3] She was now recognised as a prominent young poet and the Polish National Radio offered her a job to create and lead a team to broadcast The Radio Song Studio.

[4] Her lyrics were set to music by such composers as Krzysztof Komeda, Seweryn Krajewski, Adam Sławiński, Zygmunt Konieczny, and others.

[7] In 2013, the National Bank of Poland (NBP) issued two commemorative coins (2 and 10-zloty denominations) as part of the "History of Polish popular music" series honouring Osiecka.

[8] In 2020, the Polish public broadcaster Telewizja Polska released an eponymous biographical mini-series chronicling the life and work of Osiecka.

[9] From May 2024, the manuscript of text of song Małgośka from the collection of the National Library of Poland is presented at a permanent exhibition in the Palace of the Commonwealth.