High-mass binary stars are known to show an unexplained discrepancy between the dynamical masses of the individual components and those predicted by models. In this work, we study Sigma Scorpii, a double-lined spectroscopic binary system consisting of two B-type stars residing in an eccentric orbit. The more massive primary component is a β Cep-type pulsating variable star. Our analysis is based on a time-series of some 1 000 high-resolution spectra collected with the coralie spectrograph in 2006, 2007, and 2008. We use two different approaches to determine the orbital parameters of the star; the spectral disentangling technique is used to separate the spectral contributions of the individual components in the composite spectra. The non-LTE based spectrum analysis of the disentangled spectra reveals two stars of similar spectral type and atmospheric chemical composition. Combined with the orbital inclination angle estimate found in the literature, our orbital elements allow a mass estimate of 14.7±4.5 M ⊙ and 9.5±2.9 M ⊙ for the primary and secondary component, respectively. The primary component is found to pulsate in three independent modes, of which two are identified as fundamental and second overtone radial modes, while the third is an l = 1 non-radial mode. Seismic modelling of the pulsating component refines stellar parameters to 13.5 +0.5 −1.4 M ⊙ and 8.7 +0.6 −1.2 M ⊙ , and delivers radii of 8.95 +0.43 −0.66 R ⊙ and 3.90 +0.58 −0.36 R ⊙ for the primary and secondary, respectively. The age of the system is estimated to be ∼12 Myr. ⋆ Postdoctoral Fellow of the Fund for Scientific Research (FWO), Flanders, Belgium † Postdoctoral Fellow of the Fund for Scientific Research (FWO), Flanders, Belgium the B1 giant star with the dominant period being about 0.25 days. Both studies reported about variability in the γ-velocity which was interpreted as evidence of a companion star. The orbital solution obtained by Levee (1952) and Struve et al. (1955) independently revealed an orbital period of about 33 days, though very different eccentricities of 0.2 and 0.36, respectively. In both cases, the dominant period of ∼0.25 d was attributed to stellar pulsations. Struve et al. (1955) additionally reported a period increase with the rate of 2.3 s cen −1 . Using the RVs collected by both authors, Fitch (1967) classified the star as a single-lined spectroscopic binary and reported an orbital solution in agreement with the findings by Struve et al. (1955), including a high eccentricity value of ∼0.4. Osaki (1971) argued, however, that the variability of the γ-velocity reported by Levee (1952) and Struve et al. (1955) is not necessarily connected to the existence of a stellar companion but might be related to non-radial pulsations.Stars are expected to show slow changes in their dominant pulsation period in the course of the hydrogen exhaustion phase,