Infrared (IR) sensors are needed for ballistic missile defense (BMD). BMD IR sensor applications extend from surveillance using ground, airborne and space-based platforms, to both endo- and exo-atmospheric interceptor seekers. Even though IRFPAs using material systems, such as HgCdTe and InSb, are adequate for most tactical military applications, certain IR systems for BMD have much more stringent requirements. With a cold dim target a long distance away, IR sensors having extended wavelengths are needed in the mid course. The requirements of BMD IR sensors with high sensitivity, large format, small pixel size and high frame rate, plus long cutoff wavelength and operating at low temperatures present great challenges to IR sensor technology. This presentation will cover the current MDA IR sensor technology development, its system application for block upgrades and advanced concepts.