Sven Unterwaldt was born in Lübeck in 1965 and started his career with the TV comedy "Anfängerpech". After having been hired by cable channel RTL, he wrote and directed various sketches for Hape Kerkeling, Ingolf Lück and Wigald Boning. Since 1994, Unterwaldt has been a freelance director and he has worked on comedy shows like "RTL Samstagnacht" or "Switch".

In the following years, Unterwaldt directed other comedy programs such as Anke Engelke's TV series "Anke" that was nominated for a Grimme-Preis in 2001. In 2002, his first feature film "Wie die Karnickel", a sex comedy based on a Ralf König comic, opened in the theaters. His next movie "7 Zwerge – Männer allein im Wald" ("7 Dwarves", 2004) turned out a huge commercial success. With "Siegfried" (2005) he also spoofed classical material.

For the sequel to the "7 Dwarves" movie, "Der Wald ist nicht genug" ("7 Dwarves – The Wood is Not Enough", 2006), he again gathered the cast of seven established comedians and had Otto Waalkes as well as Bernd Eilert co-author. With Atze Schröder who had already taken part in the first "7 Dwarves" adventure, the director then made a parody of "Das Boot" titled "U-900" (2008). With a mere 200.000 admissions, the film was a lesser success at the box office compared to the Underwaldt hits that came before it.

Afterwards he teamed up with Otto Waalkes again to make "Otto's Eleven" (2010), a spoof of the successful "Ocean's Eleven" franchise. Despite mixed reviews, the slapstick type movie performed well with the audience.

For the TV series "Die ProSieben Märchenstunde" Unterwaldt adapted the fairy tale "Kalif Storch" (2012) with Elyas M'Barek as the lead. He then shot the comedy "Hilfe, ich hab meine Lehrerin geschrumpft" ("Help, I Shrunk My Teacher", 2015) which opened in theaters December 2015. In summer 2016 followed "Antonio, ihm schmeckt's nicht" ("Antonio in Wonderland"), a sequel to "Maria, ihm schmeckt's nicht!" ("Maria, He Doesn't Like It!", 2009) the hit comedy based on the novel by Jan Weiler, starring Christian Ulmen and Mina Tander.

Following this, Unterwaldt shot "Schatz, nimm Du sie!", a German remake of the popular French comedy film "Papa ou Maman" ("Mama gegen Papa", 2015) about a couple that wants to get a divorce, but neither of them wants to take the children. The animation film "Tabaluga - Der Film" (2018) is based on a musical show by rock singer Peter Maffay.

In summer 2018, Unterwaldt started shooting his next feature film "Sprite Sisters - Vier zauberhafte Schwestern", a family fantasy adventure film with a prominent cast.