The Kaldheim set becomes legal for sanctioned Constructed play on its official release date, Friday, February 5, 2021. At that time, the following card sets will be permitted in the Standard format: Throne of Eldraine, Theros Beyond Death, Ikoria: Lair of Behemoths, Core Set 2021, Zendikar Rising, and Kaldheim.

Cards found in Kaldheim draft boosters and theme boosters will be included in the Standard format. These cards are numbered 1–285 and have printed set code KHM. There are twenty additional Kaldheim cards found in set boosters and theme boosters that are also legal in the Standard format. These cards are numbered 374–393 and also have printed set code KHM.

There are sixteen new cards printed in the Kaldheim Commander Decks. These cards are legal for play in the Commander, Vintage, and Legacy formats. They aren't legal for play in the Standard, Pioneer, or Modern formats. These cards are numbered 1–16 and have printed set code KHC. The other cards in these decks are legal for play in any format that already allows those cards; that is, appearing in these decks doesn't change a card's legality in any format. Those returning cards are numbered 17–119 and have printed set code KHC.