The microwave spectra of the two 79 Br and 81 Br isotopic species of 2-bromothiophene have been measured in the region 18000-40000 MHz. For both isotopic species, the rotational constants of the ground state and one vibrationally excited state were determined, as well as the centrifugal distortion coefficients of the ground state. The ground state rotational constants in MHz are as follows: C 4 H 3 32 S 79 Br C 4 H 3 32 S 81 Br A = 5403.432 ±0.111 5403.563 ±0.095, B = 1139.0689±0.0010 1126.5173±0.0011 C = 940.5142±0.0018 931.9315±0.0009. In order to perform a second-order perturbation treatment of the quadrupole interaction, the matrix elements of products of direction cosines in terms of the symmetric top wave functions have been derived. By the first-and second-order perturbation analysis of the hyperfine splittings of the rotational lines, the nuclear quadrupole coupling constants have been determined. The values in MHz are X aa = 592.7 ±1.5 493.7 ±1.5, X bb = -295.3 ±0.6 -245.6 ±0.7, X cc = -297.4 ±1.6 -248.1 ±1.6, X ab = 80 ±9 64±8 , in the principal axes system of the molecule.