Its seat is the village of Puszcza Mariańska, which lies approximately 10 kilometres (6 mi) south-west of Żyrardów and 52 km (32 mi) south-west of Warsaw.

The gmina covers an area of 142.41 square kilometres (55.0 sq mi), and as of 2006 its total population is 8,411.

The gmina contains part of the protected area called Bolimów Landscape Park.

Gmina Puszcza Mariańska contains the villages and settlements of Aleksandria, Bartniki, Bednary, Biernik, Budy Wolskie, Budy Zaklasztorne, Budy-Kałki, Długokąty, Długokąty Małe, Emilianów, Górki, Grabina Radziwiłłowska, Huta Partacka, Kamion, Karnice, Korabiewice, Lisowola, Marianów, Michałów, Mrozy, Niemieryczew, Nowa Huta, Nowy Karolinów, Nowy Łajszczew, Olszanka, Pniowe, Puszcza Mariańska, Radziwiłłów, Sapy, Stara Huta, Stary Karolinów, Stary Łajszczew, Studzieniec, Waleriany, Wilczynek, Wincentów, Wola Polska, Wycześniak, Wygoda and Zator.

Gmina Puszcza Mariańska is bordered by the town of Żyrardów and by the gminas of Bolimów, Kowiesy, Mszczonów, Nowy Kawęczyn, Radziejowice, Skierniewice and Wiskitki.