Every M Gengar card we price, most valuable first. Prices are what copies actually sold for, updated daily.
The same Pokemon is also printed as Gengar, Mega Gengar and Gengar & Mimikyu, priced separately because the game treats them as different cards.
What a M Gengar card is worth
The most valuable M Gengar on this list is M Gengar EX (121 Secret Rare) from XY - Phantom Forces at $509.05£383.13€448.30, and the 3 priced copies across 2 sets are worth $943£710€831 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.
The highest PSA 10 on record for M Gengar sold for $9,201£6,925€8,103. Rarities here include Secret Rare.
If you are trying to identify which M Gengar 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: XY - Phantom Forces, XY Promos.