N2‐broadened linewidths of NO in the 5.4 μ band have been measured. This provides a means of determining the quadrupole moment of NO, which has been poorly measured so far. Using the Anderson–Tsao–Curnutte theory of line broadening, and this new value, 2.4×10−26 esu⋅cm2, for the quadrupole moment of NO, self‐broadened and foreign‐gas (N2 and O2) ‐broadened linewidths of NO at 300°K for all important infrared transitions are calculated. In the self‐broadening calculations, dipole–dipole, dipole–quadrupole, quadrupole–dipole, quadrupole–quadrupole, induced, and dispersion interactions were taken into account. For the case of foreign‐gas broadening, dipole–quadrupole, quadrupole–quadrupole, dipole–hexadecapole, quadrupole–hexadecapole, induced, and dispersion interactions were considered. Air‐broadened linewidths of NO have also been computed at 200, 250, and 300°K.