Known as a human settlement with 'healing waters' since the beginning of the 16th century, the town borrowed its name from a Romanian landowner, Toma Olanescu, who, after 1760, provided the spa with its first bathing facilities.
In 1829, Olanesti was already known to both patients and physicians as the curing qualities of its sulphurous water springs for instance matched those of famous spas like Baden, Saint-Sauver, Aix-les-Bains, Aix-la-Chapelle, Wiesbaden, Vichy, Vals, Ems and Bourboule.
In the 19th century a lot of medical research-work has been carried on the therapeutic results of the spring waters in Olanesti, which were actually acknowledged in Europe in 1873, when the spa was awarded a Golden Medal at a World Exhibition held in Vienna.
Since then, the mineral waters of Olanesti have been widely recommended in the treatment of disorders of the digestive system and of the related glands, of the kidneys, of the urinary duct, of the locomotory system, of the peripheral nervous system, as well as in the therapy of professional diseases, metabolic and nutritive affections, otorhinolaryngological, dermatological and associated maladies.
In 1922 the catchment of 22 mineral water springs was benefited by the assistance of a specialized company in Vienna. Chemical analyses on the radioactivity and alkalinity of the mineral waters in Olanesti led to the conclusion that they were as effective as those in Karlsbad, Evian, Thonon, Contreseville, Martigni, Vittel, Baden, Aix-les-Bains, Wiessbaden etc.
In 1930-1944 private Romanian banks provided financial support for the modernization of the resort.
A sanatorium was built in 1951-1954, whereas the town's sewage and spring water catchment systems were restored in 1975.