A simple theoretical model of the tropical troposphere is used to study whether boundary layer friction is destabilizing to the Madden–Julian oscillation (MJO) and other convectively coupled moist equatorially trapped Kelvin-like modes. A linear stability analysis is performed on an equatorial beta plane with a continuously stratified atmosphere using a Betts–Miller-like convective parameterization. The troposphere is divided into a frictional boundary layer close to the surface and a frictionless free troposphere. The basic state is horizontally homogeneous and uniformly convecting. The full linear stability problem can be discretized into an eigenvalue problem that is barely computationally tractable. A scaling analysis appropriate for low-frequency, long wavelength modes, such as the MJO, leads to a much simpler eigenvalue problem. Friction is found to be modestly destabilizing for the moist Kelvin mode, increasing its growth rate by 0.03 day−1. It also has a smaller destabilizing effect on th...