Born in Königstein im Taunus, Peter Knaack trained at the Otto Falckenberg Schule (1990–1993). Early engagements included Städtische Bühnen Freiburg and Nationaltheater Mannheim. He worked under Christoph Marthaler at Schauspielhaus Zürich and later at Maxim Gorki Theater Berlin and Schauspiel Frankfurt. At Schauspiel Hannover (2004–2009), he collaborated with Jürgen Gosch. He was an ensemble member at the Wiener Burgtheater (2009–2019), working with Jan Bosse and Matthias Hartmann.
Since 2019, he freelanced (guest appearances at Schauspiel Köln/Theater Basel) and performed in opera («Der Freischütz», 2025). Film credits include «Yella» (Christian Petzold) and «Heart of Light» (with Tilda Swinton). He returns to the Schauspielhaus Zürich ensemble in 2025/26.