Boron oxide is a key component to tailor the softening temperature and viscosity of the sealing glass for solid oxide fuel cells (SOFCs). The primary concern regarding the use of boron-containing sealing glasses is the volatility of boron species, which possibly results in cathode degradation. In this paper, we report the role of volatile boron species on the electrochemical performance of LSM/yttria-stabilized zirconia (YSZ) and LSCF cathodes at various SOFC operation temperatures. The transport rate of boron, ∼3.24× 10 -12 g/ cm2 sec was measured at 750°C with air saturated with ∼3% moisture. A reduction in power density was observed in the cells with the LSM/YSZ cathodes after the introduction of boron source to the cathode air stream. A partial recovery of the power density was observed after the boron source was removed. Results from post-test secondary-ion mass spectroscopy (SIMS) analysis showed that the partial recovery in the power density correlated with the partial removal of the deposited boron by the clean air stream. The presence of boron was also observed in the LSCF cathodes by SIMS analysis; however, the effect of boron on the electrochemical performance of the LSCF cathode was negligible. The coverage of triple phase boundaries in LSM/YSZ was postulated as the cause for the observed reduction in the electrochemical performance. © 2010 the Electrochemical Society.