Previously known as Yazhou-fu, the city is first mentioned during the Zhou Dynasty (1122-255 BCE). It served as a county seat during the Qin and Han Dynasties, but was subsequently taken by nomadic tribes. After being reintegrated into the Chinese Empire in the late 5th century, it was made the seat of the Ya Prefecture in 604. The modern Ya'an county was established in 1912. It became the provincial capital of Xikang province in 1951, but has been a municipality under the administration of Sichuan province since 1955, when Xikang province was merged and became a part of Sichuan province.

The first giant panda was found in Baoxing County of Ya'an; Ya'an is also the origin of Artificial planting tea of the world； Mengding Mountain in Mingshan County, has been keeping seven tea trees, which are believed to be the origins of tea, for more than 1,000 years.

"The busy little town [of Yaan] was full of life, for its market is the only trading centre for the Chinese and Tibetans from Kangting. Accompanied by two coolies, I crossed the long suspension bridge which oscillates alarmingly over the Ya Ho. I got separated from my coolies in the dense crowd which swarmed along the main street, but in the end found them, and my luggage, at the Catholic mission, where two venerable fathers welcomed me with the flowery courtesy of mandarins...

Yaan is the main market for a special kind of tea which is grown in this part of the country and exported in very large quantities to Tibet via Kangting and over the caravan routes through Batang (Paan) and Teko. Although the Chinese regard it as an inferior product, it is greatly esteemed by the Tibetans for its powerful flavor, which harmonizes particularly well with that of yak butter and salt which Tibetans often mix with their tea. Brick tea comprises not only what we call tea leaves, but also the coarser leaves and some of the twigs of the shrub, as well as the leaves and fruit of other plants and trees (the alder, for instance). This amalgam is steamed, weighed, and compressed into hard bricks, which are packed up in coarse matting in subunits of four. These rectangular parcels weigh between twenty-two and twenty-six pounds—the quality of the tea makes a slight difference to the weight—and are carried to Kangting by coolies. A long string of them, moving slowly under their monstrous burdens of tea, was a familiar sight along the road I followed."