It is unlikely that the line was ever particularly viable, since it ran through a rural area without any town of any size, largely following the route of an old military road. Some of the stations were not particularly near the village they served e.g. Drymen station was really in the smaller village of Croftamie, and Balfron station was not very near Balfron (probably the largest village on its route) which led to a hamlet of Balfron Station growing up at the station.
The line was closed as a through route for passenger traffic on 1 October 1934, quite some years before the Beeching Axe, although the Strathendrick and Aberfoyle Railway remained open for passenger traffic until 1951. The various sections were then progressively closed to passengers and freight:
1 November 1950
Closed for freight
Drymen to Gartness Junction, and Buchlyvie Junction to Mye Siding