The event is being delivered by Wollondilly Shire Council and Transport Heritage NSW, the operators of the NSW Rail Museum.
Visitors can enjoy steam train rides on the State's rail heritage collection, demonstrations by local artisans, and a colorful annual street parade.
This year's festival includes the return of the iconic Huff n’ Puff race, which gives runners the chance to race against the beautifully refurbished 3001 engine.
There will also be an expansion of Saturday's activities, a family carnival, and a performance by Chris Sebastian, winner of The Voice 2020.
At least six historic engines will be in steam throughout the weekend at the NSW Rail Museum, including Locomotive 3001, which was recently restored by THNSW volunteers and staff.
The festival promises a range of activities, including steam train rides, cab visits, steam machinery, live steam models, and more.
The NSW Rail Museum will be open on Saturday, and the family carnival will take place at Thirlmere Sportsground, while on Sunday, the village will come to life with market stalls, a street parade, live performances, and other activities at the NSW Rail Museum.
Wollondilly Mayor Matt Gould said that the council is proud to host the State's premier steam event once again and encouraged everyone to participate in the fun.
To book tickets for the train rides and find out more about the event, visit www.thirlmerefestivalofsteam.com.au