This work presents an experimental study on the gas–liquid two-phase slug flow pattern in pipes with slight direction change. On offshore seabed and onshore lands, situations where the pipeline must conform to the terrain are common, thus causing direction changes and slight flow inclinations. The slug flow tends to modify itself by changing its features or even transitioning to another flow pattern. The pipe consisted of a horizontal section followed by a 26-mm ID, 35.6-m long downward inclined section with inclinations of either −3°, −5° or −7° with the horizontal. Air and water were the working fluids. Resistive sensors were installed at three different pipe locations in order to detect both phases and to obtain the slug flow characteristic parameters. A high-speed camera was used in two different locations to visualize and identify the flow phenomena along the pipe, and to obtain slug flow parameters as well. The slug dissipation mechanism occurs because the inclined downward section accelerates the liquid film; simultaneously, the slug upstream fills the space left while it also accelerates, thus generating bubble coalescence. Three different phenomena were observed when the slug dissipation occurs: the gas plug, stratification and wave flooding. It was also observed that the bubble rear velocity (VR) tends to exceed that of its front for several experimental points when those bubbles enter the downward section and the dissipation process begins – a phenomenon poorly explained in the literature. Each phenomena can be classified through the mixture Froude number and the superficial gas and liquid velocities as functions of the inclination angle. Finally, the present work brings a twofold contribution: phenomena so far superficially discussed in the literature were detailed with the aid of average values and probability density function (PDF) and, as a central point, the use of the dimensionless Froude number to classify the occurrence of these phenomena in the dissipation process.