Hannikainen was the son of Pekka Juhani Hannikainen and the brother of Väinö Hannikainen, both of whom were composers and of Tauno Hannikainen who was a conductor. After studying at the University of Helsinki (1911–14), he became a pupil of Franz Schreker at the Musikakademie in Vienna, and continued his studies with Alexander Siloti in Saint Petersburg (1915–17) and with Alfred Cortot in Paris (1919). Returning to Finland, he taught piano at the Helsinki Conservatory and later gained a Professorship at the Sibelius Academy.
Hannikainen steered Finnish classical music from late Romanticism towards Impressionism. In addition to his piano miniatures, which best illustrated this development, he composed one opera, one piano concerto, one piano quartet, lieder, and film scores (notably, Sången om den eldröda blomman, Sweden, 1934).
In the 1970s, the Ilmari Hannikainen Pianokilpailu (Ilmari Hannikainen Piano Competition) was created dedicated to Hannikainen. In 2020, the competition renewed its format style.
- "Hietaniemen hautausmaa – merkittäviä vainajia" (PDF). Helsingin seurakuntayhtymä. Retrieved 27 August 2016.
- "Ilmari Hannikainen Pianokamarimusiikkikilpailu". Keski-Suomen Musiikin Edistämissäätiö (in Finnish). Retrieved 29 October 2021. (Translated: Ilmari Hannikainen Piano music Competition - Kesmes.com)
- Biography from Kimmo Korhonen's Inventing Finnish Music: Contemporary Composers from Medieval to Modern, Finnish Music Information Centre (2003)
- Free scores by Toivo Ilmari Hannikainen at the International Music Score Library Project (IMSLP)
- Ilmari Hannikainen at IMDb
- Songs by Ilmari Hannikainen on The Art Song Project