Parents with a Costco membership, get ready to save, because the semiannual Kirkland diaper sale is back as of Oct. 27, 2025. This time around, you can save $5 - $10 per box, depending on the size, and the deals last for a whole two weeks. These savings can add up fast if you're buying multiple boxes (the limit is three), and the discount applies automatically at checkout. And just like the deals in the Costco Coupon Book, no coupons are actually required.
We've tracked Costco deals and diaper sales for years, and we've noticed Costco typically follows a pretty consistent pattern. Here's everything to know to shop the Kirkland diaper sale like a pro.
Best Costco Diaper Sale Deals We're Shopping Through Nov. 9
During the last Costco Diaper Sale in July, the discount was $4 off size 1 diapers, so this deal got better now, with $5 - $10 off per box.
The Costco Diaper Sale is a twice-a-year, multiday event, with $5 - $10 off each box of Kirkland diapers automatically.
Costco has historically run this sale twice yearly, typically once in June and again in November. But in 2025, they didn't start the summer sale until July 14, and the fall sale kicked off Oct. 27. The discount applies to all sizes of Kirkland Signature diapers, regularly priced at $39.99 for sizes 3 and up, $19.99 for size 2, and $14.99 for size 1. Savings happen instantly at checkout, no coupons required.
Note that Kirkland recently switched from Kimberly-Clark to First Quality (the maker of Cuties diapers) and has changed box sizes and prices, so the discount structure is slightly different this year.
The Costco Diaper Sale is Oct. 27 - Nov. 9, 2025.
Costco never announces this sale in advance, but we've confirmed a Kirkland diaper sale is happening Oct. 27 - Nov. 9. The team at The Krazy Coupon Lady originally predicted we'd see another Costco Diaper Sale Nov. 10 - 16, but it looks like they moved the date up by two weeks this year.
After the fall event, the next Costco diaper sale likely won't happen until July 13 - 26, 2026, so it could be worth stocking up. However, keep in mind that the limit is three boxes during the sale.
Claim the same diaper sale prices online or in-store, but only members can shop in stores.
Unlike many of the items you can buy from Costco online, there's no online markup on diapers, meaning that the price you see for diapers on Costco.com is the same low price you'll pay in the warehouse. Plus, shipping is free on Costco diapers.
However, non-members can shop the sale online.
A Costco membership isn't required to get this deal online, but nonmembers will pay a 5% fee at checkout.
There's a limit of three boxes per member.
Costco has typically limited diaper sale purchases to two boxes per size, per membership per day. But in the fine print for the 2025 sales, there's a limit of three boxes per member.
KCL TIP: Need more boxes than the limit? Ask a friend with a Costco membership to help you stock up.
Buy enough to last awhile, as the sale only happens twice a year.
Since this sale only comes around once every six months, it's a good chance to stock up if you like the Kirkland brand diapers. Just calculate your monthly diaper usage and multiply that by six, but keep the limit of three boxes in mind.
Here are the current diaper counts per box:
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Size 1: 96 diapers per box
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Size 2: 112 diapers per box
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Size 3: 222 diapers per box
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Size 4: 198 diapers per box
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Size 5: 168 diapers per box
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Size 6: 132 diapers per box
Ask for a price adjustment if you bought full-price Kirkland diapers within 30 days of the sale.
Recently bought Costco diapers at full price? The Costco price adjustment policy gives you money back if an item goes on sale within 30 days of purchase.
For in-store purchases, visit the Returns desk with your membership card (no receipt needed) to get a refund for the price difference. For online orders, fill out Costco's price adjustment form on their website.
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