Parents with a Costco membership, get ready to save, because the semi-annual Kirkland diaper sale is back. We fully expected to see this sale pop up in early June, but after a few weeks of waiting, the Kirkland diaper sale is officially here as of July 14. You'll save $4 - $10 per box (25% - 27% off) during this 2-week event. 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. But with recent supplier changes, expect some differences this time around.
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The Costco Diaper Sale Deals We're Shopping
The Costco Diaper Sale is a twice-a-year, 14-day event that knocks up to $10 off each box of Kirkland diapers automatically.
Costco has historically run this sale twice yearly, typically in June and November. But in 2025, they didn't start the summer sale until Monday, July 14. 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 happening July 14 - 27, 2025.
Costco never announces this sale in advance, but as of Monday, July 14, the Costco website shows the sale prices are here through July 27 for all sizes of Kirkland diapers.
After the July event, the next Costco diaper sale likely won't happen until Nov. 13 - 19, 2025, so it could be worth stocking up on enough diapers (and sizes) to last you for six months. Keep in mind that the limit is three during the July sale.
Claim the same sale prices online or in-store.
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.
A Costco membership isn't required to grab this deal online, but nonmembers will pay a 5% fee at checkout.
There's a limit of three boxes per member.
Costco typically limits diaper sale purchases to two boxes per size, per membership, per day. But in the fine print for the July offer, it states that there's a limit of three boxes per member.
KCL TIP: Need more boxes than the limit? Ask friends with a Costco membership to help you stock up.
Buy enough to last you a while, 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 in mind.
Here's a list of the current diaper counts per box:
Size 1: 96 diapers per box
Size 2: 112 diapers per box
Size 3: 222 diapers per box
Size 4: 198 diapers per box
Size 5: 168 diapers per box
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, just 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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