Exhibit 23.1 INDEPENDENT AUDITORS' CONSENT We consent to the incorporation by reference in this Registration Statement of ManTech International Corporation on Form S-8 of our report dated November 16, 2001, except for Note 8, as to which the date is December 17, 2001, appearing in a Registration Statement on Form S-1 (No. 333-73946) of ManTech International Corporation filed with the Securities and Exchange Commission on November 23, 2001, as amended. /s/ Deloitte & Touche LLP McLean, Virginia February 27, 2002 13