The Government body has invested £863,000 to double the number of stations where travellers can go online from the 26 already getting wi-fi capability.
Previous investment has seen internet access rolled out at some of Scotland's busiest train stations, including Glasgow Central.
The second round of work, taking in Oban, Aviemore and Troon among others, is due for completion before the next ScotRail franchise begins in April next year.
ScotRail's Class 158 and Class 380 trains will also be fitted with wi-fi equipment after the operator's Class 170 trains were upgraded last year. By next spring, almost half its trains will be connected.
Transport Minister Keith Brown said: "We want to ensure all passengers can get on with their busy lives while travelling and that visitors to truly international events have a good experience of our rail networks.
"While it is great that wi-fi brings benefits for events like the Commonwealth Games and the Ryder Cup, it is equally important we have a rail network that is fit for the future as we move towards the next franchise.
"Scotland's business community has made it clear that wi-fi access on commuter routes would boost competitiveness in Scotland and we are already well on the way to ensuring online access on all of our busiest commuter routes.
"The second tranche will see relatively low-footfall stations at Wick, Kyle of Lochalsh, Oban and Aviemore all benefit, as well as other tourism-heavy stations such as Troon, Leuchars and Balloch."
Steve Montgomery, ScotRail managing director, said there are more than a quarter of a million wi-fi users on its express trains each month.
"With this in mind, we're also optimising our entire website for people using mobile devices and updating the wi-fi log-in process so people can stay connected when moving between trains and platforms," he said.