Merthyr Tydfil council handed over the running of leisure and community centres, libraries and cultural sites to the trust on Wednesday.
Merthyr Tydfil Leisure Trust, which is supported by a board of 11 trustees, took the reins after a year of public consultation.
The trust said the move would "protect the future" of such services.
It will be led by chief executive Richard Marsh.
He said: "Operating as a trust will give us lots more opportunity to access funding and provide a more flexible way of working, which in turn will allow us to provide an even better service."
A south east Wales council has transferred control of its leisure and culture services to a trust.