Mylonitization in the southern part of the Cobequid Mountains resulted from deformation of igneous and sedimentary rocks during the Devonian Acadian orogeny. Detailed analyses of mineral lineation, penetrative s-surfaces, and mineral grain fabrics suggest that uniform tectonic flow within the mylonite zone produced rock strains with extension parallel to the mineral lineation. Quartz fabrics originated when large quartz crystals deformed into elongate granular aggregates. A regional compression axis, inferred from a laminar flow model for the mylonite zone, is compatible with a compression axis derived from slickensided fractures in granitic rocks north of the mylonite zone. The subhorizontal, southeasterly trending compression axes are perpendicular to the regional trend of the Appalachians mountain chain in Nova Scotia.