Every Keldeo card we price, most valuable first. Prices are what copies actually sold for, updated daily.
What a Keldeo card is worth
The most valuable Keldeo on this list is Keldeo EX (142 Full Art) from Boundaries Crossed at $147.81£111.25€130.17, and the 32 priced copies across 17 sets are worth $387£291€340 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.
Keldeo is printed in Japanese as well: 24 cards across 17 sets, the most valuable of them Keldeo from Everyone's Exciting Battle at $55£41.40€48.44. 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 Keldeo sold for $5,493£4,134€4,837. reverse holo printings are priced separately from the standard card, because they do not trade at the same money. Rarities here include Secret Rare, Special Illustration Rare.
If you are trying to identify which Keldeo 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: Boundaries Crossed, White Flare, XY Promos.