Short answer: not really, although both start with tea
Kombucha is made from sweetened tea, often black or green, that is fermented with a culture called a SCOBY. The result tastes tart, fizzy and slightly vinegary. Green tea is simply brewed tea. The two share a starting point, but they taste quite different.
What green tea tastes like, and what kombucha tastes like
Green tea is usually described as fresh, grassy or vegetal, sometimes sweet or nutty. It is served hot or cold, without fizz.
Kombucha is tangy and sour, with a vinegary edge, and it is often carbonated. Its sweetness depends on how long it ferments and on any fruit, juice or herbs added afterward. A longer ferment usually means less sugar and a sharper taste.
How fermentation changes the tea
During fermentation, the culture uses up much of the sugar. The yeast produces small amounts of alcohol and carbon dioxide, which is where the fizz comes from. Bacteria then convert some of that alcohol into acids. This is why kombucha has a sour note that green tea does not.
Caffeine: how they compare
Both drinks come from tea, so both can contain caffeine. Green tea’s caffeine level depends on the leaf, how much you use and how long it steeps. Kombucha usually keeps some of the caffeine from its tea base, but the amount varies by brand and batch. We do not have a reliable number for every product, so check labels where they are given, or try a small glass and see how you feel.
Sugar and alcohol: what to check
Plain green tea has no sugar unless you add it. Kombucha usually contains some sugar. Much of it is used up during fermentation, but commercial products vary, and some add sugar, juice or fruit after fermentation. Check the nutrition label.
Kombucha also contains a small amount of alcohol. Commercial products are usually labeled as under 0.5%. Homemade batches can be higher and more variable. For more on this, see why you might feel buzzed after drinking kombucha.
Can you make kombucha with green tea?
Yes. Green tea makes a lighter, fresher kombucha, but it needs more care with steep time and water temperature than black tea. For a side-by-side look at the two bases, see green or black tea for kombucha.
Bottom line
Kombucha is a fermented drink that starts with tea, but it is not a type of green tea. If you like the freshness of green tea, you may enjoy a green-tea base, though you should expect a tart, fizzy drink with a different character.