Helen Ross McNabb Center officially merged with Chattanooga-based Fortwood Center on Monday.
Merger negotiations started a few months ago when Fortwood's CEO announced plans to retire after 35 years.
HRMC Senior Director of Development Houston Smelcer said Fortwood wanted to join with an organization sharing a similar philosophy.
"Fortwood center does a lot of the same things that HRMC does, and they do it like we do it," said Smelcer. "They do it well, providing quality mental health and addiction services, and they're very fiscally conservative like the HRMC."
Patient care will continue like normal at both facilities. HRMC will now employ Fortwood's staff, and together, they'll serve more than 17,000 people.