Every Koffing card we price, most valuable first. Prices are what copies actually sold for, updated daily.
What a Koffing card is worth
The most valuable Koffing on this list is Koffing (Secret) from SM - Cosmic Eclipse at $39.09£29.42€34.43, and the 27 priced copies across 25 sets are worth $286£216€252 together. Most of that sits in a handful of printings: the older the set and the scarcer the print run, the wider the gap to the rest.
Koffing is printed in Japanese as well: 29 cards across 24 sets, the most valuable of them Koffing from Intro Pack Neo (Chikorita) at $86£64.73€75.74. Switch the list above to Japanese to read those, or to Both to rank the two catalogues against each other.
The highest PSA 10 on record for Koffing sold for $765.89£576.44€674.50. 1st Edition and reverse holo printings are priced separately from the standard card, because they do not trade at the same money. Rarities here include Secret Rare.
If you are trying to identify which Koffing you have, the set name is printed on the card and the collector number sits in the bottom corner. Open the card here and the page carries every printing of it, the graded prices, and whether grading the copy is worth the fee. Sets to start with: SM - Cosmic Eclipse, EX Delta Species, EX Team Rocket Returns.