How delays are dealt with and the cost of tickets are the biggest concerns for train users, new figures show.
Independent watchdog Transport Focus interviewed 1,244 Welsh commuters in its latest survey.
Since its last poll in Autumn 2016, those satisfied with how delays are dealt with and ticket value for money have dropped by four percentage points to 38% and 57%, respectively.
But overall, 83% were satisfied with Arriva Trains Wales' service.
Satisfaction with other aspects, such as stations (76%) and crowding levels (72%) remained largely unchanged.
Noting other points, Anthony Smith, the watchdog's chief executive, said: "Arriva Trains Wales passengers have clocked an improvement in satisfaction with aspects of their stations including the availability of staff.
"They are also happier with ticket buying facilities, cleanliness and personal security at stations."
The watchdog said results were in line with another recent survey it carried out relating to what passengers expect when a new rail contract is awarded in October 2018.
Four companies, including Arriva Trains Wales, are competing to run the Wales and Border franchise and develop a South Wales Metro system.
Mr Smith said passengers appreciated service from staff and wanted to see more seats on better quality trains.
Barry Lloyd, head of customer experience for Arriva Trains Wales, said: "The fact we've improved in these areas shows we've really listened to customers from past surveys, investing in new technology for ticket buying and training our staff to give the best service possible.
"Our mobile phone tickets, new machines on stations and longer booking office opening hours are testimony to this as well as multiple examples of great service by our staff week in week out and during the Champions League, which attracted national media coverage."