Gwent is a turn-based card game between two players that can last two to three rounds. Players play one card each turn from a hand of 10 cards, chosen from a deck of 25. Each deck belongs to one of six factions that offer different play styles. In contrast to The Witcher 3: Wild Hunt's variation of Gwent, the Siege row is removed, leaving two rows where cards can be played: the Melee and Ranged rows.

The goal is to win two of three rounds by playing cards to gain points called "power" on the board. Each card has a certain power (which can be boosted or reduced), resulting in the player's points being the total of all of their cards. A player wins a round by having more points on board than their opponent. Each card can potentially have multiple special abilities, such as the ability to damage other units on deployment, boost other units' point value, spawn other units when given conditions are met, trigger an effect when destroyed, and lock another card's ability. Rounds end when either both players pass to the next round, or when both players run out of cards. The first to win two out of three rounds wins the game.

Each deck is built with a chosen faction combined with a unique leader ability. The deck will have a 150 Provision Limit plus the Provision the leader adds on. A minimum of 25 cards is required, with at least 13 of those being unit cards that are played on the field and have power (as opposed to special/artifact cards which are discarded upon use or remain on the field with no power). Each card has a Provision Cost, and only neutral cards and cards from the selected faction can be added to a deck. Decks are made up of bronze cards, which the player can have two copies of in their collection and deck, and gold cards, of which players can only own one copy.

Round wins go toward daily quests and Gwent's battle pass system, Journey. Rewards include crafting materials for cards and card packs, or "kegs," which can also be purchased through microtransactions. Each keg contains five cards, with the first four being of lower rarity and the fifth being of higher rarity and selected from a spread of three cards. Players can also craft the animated, or Premium, versions of their cards. Using the "Good Game" button after matches also rewards crafting materials. Players are also awarded currency which can unlock nodes in the Reward Book, which unlocks cosmetics like avatars and other crafting materials or currency for kegs.

The game features several modes of gameplay. Ranked Play matches players of similar rank and allows them to progress and regress through tiers, while Casual Play allows players to be matched against anyone without loss penalties. Ranked takes place across a month-long season where players aim to increase in rank for better end-of-season rewards. Player ranks work on a numerical system from 1-30, with a new player starting at rank 30. A player ranks up after accumulating 5 wins (or "Mosaic Pieces"), with a loss lowering the win counter by 1. Win streaks are available until rank 7. After ranking up from rank 1, players achieve 'Pro Rank', the entry point of Gwent Official Competitive Play, with invites to Gwent Open qualifiers for players in the top 64 of the Pro Rank Leaderboard. At the end of each monthly season, players de-rank by two from their current standing (ex. going from rank 7 to rank 9). This also applies for Pro Rank, where if players do not finish within the top 500, they will be reset to Rank 3 for the next season.

The level system works on a numerical scale of 1-60, with no effect on ranking or matchmaking. Players automatically "prestige" after reaching level 60, which grants them permanent account rewards such as guaranteeing a rare card within the first 4 cards of a keg. Players can currently level up to Prestige 10.[7] Certain gamemodes are locked behind a level requirement, such as the rotating seasonal mode requiring level 10 to play.

Players are also assigned a matchmaking rating for each faction, which respectively increases or decreases as a player wins and loses games. When entering Pro Rank, this rating is set to a base of 2400 for all factions. A general matchmaking rating (used for leaderboard ranking) is then calculated from the average of their 4 best performing factions where they have played at least 25 matches for a faction to be considered at 100% of its rating, with the faction rating being used being their peak rating for that faction.