Cold Brew Oolong Tea

Reviewed by the Oolong Tea Home editorial desk·Published October 15, 2026·Reviewed October 15, 2026

Cold brewing is the one method where you deliberately start with a long steep, because cold water extracts so slowly that there is almost nothing to over-extract. Where a hot infusion is measured in seconds, a cold one is measured in hours, and the cup that comes out is sweeter and less bitter than the same leaf brewed hot and then chilled. That difference is not imagination. The compounds that taste bitter dissolve far more readily in hot water, and at fridge temperature most of them stay in the leaf.

Ratio and time

Whole leaf is the right starting point. Broken leaf and dust cold brew into a bitter, cloudy liquid within a couple of hours, because the extraction surface is far larger. If the leaf is very tightly rolled, give it the longer end of the range — a pellet oolong needs time to unfurl even in cold water.

Which oolongs cold brew well

Light, unroasted oolongs are the best candidates: high-mountain Taiwanese tea, green-style Tieguanyin, Baozhong and Jin Xuan. Their floral and creamy notes survive cold extraction and come across cleanly, and the sweetness that can hide behind the heat in a hot cup is much more obvious at fridge temperature.

Heavily roasted Wuyi teas are the wrong choice. The roasted, mineral, toasty character that makes Rou Gui and Da Hong Pao worth drinking is partly a function of temperature — served cold, the same tea tastes thin and slightly ashy. If you want an iced drink from a roasted oolong, brew it hot and strong, then chill it quickly. That is a different technique with a different result, and it keeps the roast intact.

How to make it

1. Weigh the leaf. Five grams per 500 ml is the standard ratio. A heaped teaspoon of rolled leaf is roughly right if you have no scale.
2. Add cold water. Filtered water tastes better here than tap, because there is nothing else in the drink to mask an off note. Room-temperature water is fine too and extracts a little faster.
3. Refrigerate for 8 to 12 hours. Leave it overnight. There is no benefit to shaking it, and no risk in leaving it a few hours longer.
4. Strain the leaf out. Pour through a fine sieve or a strainer bag into a clean bottle. Leaving the leaf in makes the drink keep getting stronger and eventually bitter.
5. Drink within 2 to 3 days. Keep it sealed and cold. It does not spoil quickly, but the aroma fades and the drink starts to taste flat.

The leaf can be brewed a second time. A second cold steep of the same leaf, run 12 to 18 hours, comes out lighter but still worth drinking, which brings the cost per litre down considerably.

Cold brew is not iced tea

The two get treated as the same drink and they are not. Iced tea is normally brewed hot and concentrated, then poured over ice or chilled, which extracts the full bitterness and caffeine profile and then dilutes it. Cold brew never applies heat at all, so the cup is smoother and lower in caffeine from the start. If you want the aroma of a hot oolong in a cold drink, brew hot and chill. If you want something clean and sweet to drink through the day, cold brew it.

How much caffeine is in it

Less than a hot cup of the same tea, and the difference is large. Cold water extracts caffeine slowly and incompletely over the 8 to 12 hours, so a cold-brewed oolong typically carries a fraction of the caffeine the same leaf gives up in a hot infusion. That makes it a reasonable choice in the evening, when a hot oolong would keep you up. The per-cup hot figures are on the oolong tea caffeine page.

Common problems

It tastes weak. Cold extraction is slow, so a light ratio reads as water. Add leaf rather than time — doubling the time past twelve hours mainly adds bitterness, not flavour.

It tastes bitter anyway. Usually broken leaf or dust, which has far more surface area than whole leaf and extracts much faster in cold water. Switch to whole leaf, or cut the steep back to six hours.

It went cloudy. Cold brewed tea can turn hazy when it is chilled further or left too long, because some of the extracted compounds come out of solution. It is harmless, and it settles if the bottle is left to stand, though it will not clear completely.

It tastes of the fridge. An open jug picks up whatever else is in there. Keep it sealed, and keep it away from strong-smelling food.

Serving it

Cold brewed oolong is best drunk as it is, over a single large ice cube if you want it colder still. Because the bitterness is already low, it does not need sweetening, and sugar tends to flatten what aroma is left. A slice of citrus or a sprig of mint works with the lighter, more floral oolongs and fights the roasted ones, which is another reason not to cold brew them. For a sparkling version, dilute the concentrate with cold sparkling water about one to one rather than carbonating the tea itself, which foams badly and loses its aroma.