Exhibit 21

List of Subsidiaries
The following is a list of subsidiaries of Monitronics International, Inc., the names under which such subsidiaries do business, and the state or country in which each was organized, as of March 18, 2021. The list does not include dormant subsidiaries or subsidiaries which would not, if considered in the aggregate as a single subsidiary, constitute a significant subsidiary within the meaning of Item 601(b)(21)(ii) of Regulation S-K.
SubsidiaryJurisdiction of Formation
Monitronics International, Inc.Delaware
Monitronics Canada, Inc.Delaware
MI Servicer LP, LLCDelaware
MIBU Servicer, Inc.Delaware
Monitronics Security LPDelaware
Monitronics Funding LPDelaware
Platinum Security Solutions, Inc.Delaware
Security Networks LLCFlorida
LiveWatch Security, LLCDelaware