The number of trains from Glasgow to Oban will increase to six a day in each direction, although the journey will still take around three hours.
The first train will leave the Argyll town at 5.21am, arriving in Glasgow at 8.37am. One which departs Glasgow Queen Street at 5.20am will reach Oban just after 8.30am.
There will also be extra services in the afternoon and the evening. The new service leaving Oban at 8.37pm will connect with the southbound Caledonian Sleeper from Fort William at Crianlarich, where travellers heading to London can get sleeper berths.
Transport Minister Keith Brown said: "By doubling the trains on the route, we offer regular commuters more travel options and provide the local economy with a boost by making it even easier for visitors to get a taste of the fantastic tourist offering in Argyll and Bute. These additional services will also improve connections to one of Scotland's busiest ferry ports, bringing similar benefits to the island economies in the Inner and Outer Hebrides."
Duncan Macintyre, Independent councillor for Oban North and Lorn who is also a board member of the Highlands and Islands transport partnership HITRANS, said: "The opportunities range from daily commuting into Oban from stations from Crianlarich to Connel Ferry to day trips to Glasgow for work, education and leisure. The last train of the day, the 8.36pm from Oban, arrives in Glasgow in less than three hours."