A storm water drain filter including a collapsible frame supporting a filter bag. The filter may be installed in a stormwater drain pit to capture contaminants and particulate matter before it enters a stormwater drain. The collapsible frame is light weight, compact, simple and inexpensive. The filter bag is secured to the frame so as to maintain its shape and avoid deformation. There is also disclosed a method of installing a stormwater drain filter in a stormwater drain pit to provide an effective seal between the stormwater drain filter and the pit.