Best credit card for Costco in Canada: the Mastercard-only rule and how to maximize it

If you shop at Costco in Canada, your card choice is made for you at the door: Costco warehouses and gas bars accept Mastercard only. Visa and American Express do not work in-store, no matter how good their rewards are. So the real question is not "which card has the best grocery rate," it is "which Mastercard earns the most on a Costco run, and what should I pair it with for everything else."

This guide covers the Mastercard-only rule, the official Costco co-brand card, the best Mastercards to carry for the warehouse itself, and the pairing strategy that stops Costco from quietly capping your rewards. Nothing here is financial advice, and card terms change. Always confirm payment rules on Costco's site and card details on the issuer's official page before you apply.

The rule that decides everything: Mastercard only

Inside a Canadian Costco warehouse and at Costco gas bars, the only credit card network accepted is Mastercard. You can also pay with debit, cash, or a Costco Shop Card, but Visa and American Express are not accepted in-store. This is a network-level deal between Costco Canada and Mastercard, so it applies to every Mastercard regardless of issuer.

Two consequences follow:

1. A great Visa or Amex is useless at the Costco checkout. If your main rewards card is a Visa Infinite or an Amex Cobalt, it earns nothing on your warehouse spend. You need a Mastercard in the wallet specifically for Costco.
2. Costco.ca is different. The online store accepts a broader range of cards. The Mastercard-only restriction is an in-warehouse and gas-bar rule, not a company-wide one.

The official co-brand: CIBC Costco Mastercard

The CIBC Costco Mastercard is the only card co-branded with Costco in Canada. It carries no annual fee and pays cash back as an annual certificate redeemable at Costco warehouses. Its earn structure:

• 3% at restaurants and on Costco gas
• 2% at other gas stations, EV charging, and on Costco.ca
• 1% on everything else, including general purchases inside the warehouse

That last line is the catch. The co-brand card is strong on dining and gas, but it earns only 1% on the actual warehouse run (groceries, household goods, the bulk of what most people buy at Costco). For a card built around Costco, the in-warehouse rate is its weakest category.

Best Mastercards to actually use at the warehouse

Because the co-brand pays just 1% on warehouse purchases, a different Mastercard often earns more on the same spend:

• Rogers Red World Elite Mastercard — a flat 2% back on all purchases (redeemed within the Rogers ecosystem), plus 3% on U.S.-dollar spend. With no annual fee, a flat 2% on everything beats the co-brand's 1% on the warehouse run, and there is no category guessing.
• BMO CashBack World Elite Mastercard — 5% on groceries (up to a monthly cap), 4% transit, 3% gas. The catch: Costco warehouse purchases do not always code as "groceries," because Costco is classified as a warehouse club rather than a supermarket. When the 5% applies it is excellent; when it does not, you fall to the base rate. Confirm how your purchases code before relying on the 5%.

The honest takeaway: for the predictable warehouse run, a strong flat-rate Mastercard (like a 2%-on-everything card) is the safest high earner, while a category card can beat it only if your Costco spend reliably triggers the bonus rate.

The pairing strategy

The smart setup is two cards, not one:

1. A Mastercard for Costco (warehouse, gas bar) — your best flat-rate or reliably-coding category Mastercard.
2. Your best overall card for everywhere else — which can be any network, including the Visa or Amex that earns far more on groceries, dining, or travel than Costco's network rules will ever let you use in-warehouse.

This way Costco's Mastercard-only rule costs you nothing: you simply pull the Mastercard at the warehouse and your top card everywhere else. If you want to keep it to a single card, see our guide on the best second card to pair and two-card strategies.

How to choose

• You want one no-fee card and shop Costco often: the CIBC Costco Mastercard is reasonable for the dining and gas rates, even if the warehouse rate is only 1%.
• You want the most cash back on the warehouse run: carry a flat-rate 2% Mastercard for Costco and pair it with your best card elsewhere.
• Your Costco purchases code as groceries: a category Mastercard with a high grocery rate can win, but verify the coding first.

Compare every Mastercard cash back option side by side on our cash back cards and no annual fee rankings, and check the live welcome offers before you apply. Always confirm the current earn rates, caps, and Costco's accepted payment methods on the official pages.