[2] Oja's diploma roles included Father of Toulon in Peter Barnes' Red Noses (2010), Joseph Wykowski in Neil Simon's Biloxi Blues, and Argante in Molière's The Imaginary Invalid (2011).
[6] Pääru Oja's first film appearance was in the role of Kristjan in the 2010 short Ei oska filmi teha, directed by Hardi Keerutaja and featuring Mikk Jürjens and Viire Valdma.
Set in World War II, the film is shown through the eyes of Estonian soldiers who had to choose sides and thus fight against their fellow countrymen.
[8] The following year, he appeared as Siim in the Toomas Hussar directed political thriller Luuraja ja luuletaja, starring Jan Uuspõld.
[10] In 2020, Oja had a starring role as Rupi in the Veiko Õunpuu directed joint Estonian-Finnish comedy crime-drama Viimased, shot on location in Lapland.
[11] The same year, he appeared in the role of Peeter Parik in the Margus Paju directed World War II spy film O2.
[13] In 2024, he appeared in a starring role as a fictionalized version of poet Juhan Liiv in the Jaak Kilmi directed and Indrek Hargla penned period crime drama feature film Vari.