EXHIBIT 21.1

Subsidiaries of the Company

1st Tier



| |  | ManTech Command Control Systems Corporation, a Virginia corporation
| | - | -------------------------------------------------------------------

| |  | ManTech Information Systems &Technology Corporation, a Virginia corporation
| | - | ---------------------------------------------------------------------------

| |  | ManTech Security & Mission Assurance Corporation, a Delaware corporation
| | - | ------------------------------------------------------------------------

| |  | ManTech Solutions & Technologies Corporation, a Virginia corporation
| | - | --------------------------------------------------------------------

| |  | ManTech Systems Engineering Corporation, a Virginia corporation
| | - | ---------------------------------------------------------------

| |  | ManTech Environmental Corporation, a Virginia corporation
| | - | ---------------------------------------------------------

| |  | ManTech Support Technology, Inc., a Virginia corporation
| | - | --------------------------------------------------------

| |  | NSI Technology Services Corporation, a California corporation
| | - | -------------------------------------------------------------

| |  | ManTech Advanced Systems International, Inc., a Virginia corporation
| | - | --------------------------------------------------------------------

| |  | ManTech Telecommunications and Information Systems Corporation, a Delaware corporation
| | - | --------------------------------------------------------------------------------------

| |  | ManTech Europe Systems Corporation, a Virginia corporation
| | - | ----------------------------------------------------------

| |  | ManTech Australia Pty. Ltd., a corporation organized and existing under the laws of the Commonwealth of Australia
| | - | -----------------------------------------------------------------------------------------------------------------

| |  | ManTech Australia International, Inc., a Virginia corporation
| | - | -------------------------------------------------------------

| |  | ManTech U.K. Systems Corporation, a Virginia corporation
| | - | --------------------------------------------------------

| |  | ManTech Advanced Development Group, Inc., a California corporation
| | - | ------------------------------------------------------------------

| |  | ManTech Security Technologies Corporation, a Virginia corporation
| | - | -----------------------------------------------------------------

| |  | ManTech Gray Hawk Systems, Inc., a Virginia corporation
| | - | -------------------------------------------------------

| |  | ManTech GRS Solutions, Inc., a Maryland corporation
| | - | ---------------------------------------------------

2nd Tier



| |  | Technology Management Corporation, a Virginia corporation
| | - | ---------------------------------------------------------

| |  | ManTech Systems Corporation, a New Jersey corporation
| | - | -----------------------------------------------------

| |  | ManTech Systems Solutions Corporation, a Virginia corporation
| | - | -------------------------------------------------------------

| |  | MASI U.K. Limited, a corporation organized and existing under the laws of the United Kingdom
| | - | --------------------------------------------------------------------------------------------

| |  | Field Support Services Muhendislik Ltd. Sti., a corporation organized and existing under the laws of Turkey
| | - | -----------------------------------------------------------------------------------------------------------

| |  | Redesmundial, S.A., a corporation organized and existing under the laws of the Republic of Panama
| | - | -------------------------------------------------------------------------------------------------

| |  | ManTech Europe, Ltd., a corporation organized and existing under the laws of the United Kingdom
| | - | -----------------------------------------------------------------------------------------------

| |  | ManTech Test Systems, Inc., a Virginia corporation
| | - | --------------------------------------------------

| |  | ManTech Environmental Research Services Corporation, a Virginia corporation
| | - | ---------------------------------------------------------------------------

| |  | DB Data Systems, LLC, a Virginia corporation
| | - | --------------------------------------------

| |  | Gray Hawk Technology Solutions, LLC, a Virginia corporation
| | - | -----------------------------------------------------------

| |  | Hawkeye Systems, LLC, a Virginia corporation
| | - | --------------------------------------------

| |  | Symmetron Holding Corporation, a Virginia corporation
| | - | -----------------------------------------------------

3rd Tier



| |  | ManTech Advanced Recognition Limited, a corporation organized and existing under the laws of the United Kingdom
| | - | ---------------------------------------------------------------------------------------------------------------

| |  | ManTech Database Services Europe Limited, a corporation organized and existing under the laws of the United Kingdom
| | - | -------------------------------------------------------------------------------------------------------------------

| |  | Symmetron, LLC, a Virginia corporation
| | - | --------------------------------------