MS 309 begins at the western edge of the community of
Chulahoma at an intersection with
MS 4. It winds its way northwest through a mix of farmland and wooded areas for several miles, where it makes both a sharp left, and a sharp right, as it passes through the community of
Watson. The highway now enters the town of
Byhalia at an interchange with
Interstate 22 (I-22)/
U.S. Route 78 (US 78) at their exit 14, and it travels through some neighborhoods before passing directly through downtown, where it has an intersection with
MS 178. MS 309 leaves downtown as it crosses a railroad track, traveling north through more neighborhoods before leaving Byhalia at an interchange with
I-269/
MS 304 (exit 18). The highway travels northward through farmland to cross the
Coldwater River and pass through the community of
Barton, where it has an intersection with
MS 302, before coming to an end at the
Tennessee state line, with the road continuing north as Byhalia Road into the city of
Collierville. The entire length of Mississippi Highway 309 is a rural two-lane state highway, located entirely in Marshall County. ==Major intersections==