A series of six Sundays of strikes at Glasgow Central starting yesterday were called off.
Passengers on trains operated with conductors on routes to East Kilbride, Kilmarnock, Dumfries and Stranraer had been threatened with disruption.
It is understood the disciplinary incident involved an alleged “mistake” over procedures in a train departing from a station.
RMT Scotland organiser Mick Hogg said: “ScotRail has applied common sense by reinstating our guard member over their blatant misuse of disciplinary procedure."
ScotRail operations director David Simpson said: “ScotRail was clear from the outset of this issue that it was appropriate to wait until the disciplinary process had been concluded.
“We value our relationship with the trade unions and we are happy a resolution has been found that doesn’t impact on services.”