David MacBrayne chairman David McGibbon said it was exploring a potential bid for the train operator for the next franchise from 2025.
It follows ministers keenness for a public sector bid and CalMac being among the last Scottish Government-controlled transport operators.
Mr McGibbon told the Scottish Parliament's rural economy and connectivity committee: "We would be interested in at least exploring with appropriate Transport Scotland people what it would entail.
"We've not had detailed conversations but we've indicated to Transport Scotland that we are willing to talk."
However, he also conceded the firm had no experience of running railways.
Mr McGibbon said the group wanted to expand into ports and harbours as well as ferries, including abroad.
It runs the Marchwood military port complex near Southampton and has bid to run Perth Harbour.
CalMac managing director Robbie Drummond added: "We have indicated our interest in having a discussion with Transport Scotland about the possibility of us operating a rail service."
A Transport Scotland spokeswoman said: “Our consistent view over many years is there ought to be a level playing field between the private and public sector in bidding for rail franchises.
"It is vital we take the time to think through the various scenarios, as ministers want to enable a competitive public sector bid which offers best value for the public purse while delivering continuous service improvements.
"We expect an announcement to be made on this before the summer recess."