Parents with a Costco membership, mark your calendars: the next semiannual Kirkland diaper sale is predicted to happen July 13 - 26, 2026. Based on Costco's consistent sale pattern from 2025, we're anticipating you'll save $5 - $10 per box, depending on the size, and the deals should last for a whole two weeks.
These savings can add up fast if you're buying multiple boxes (the limit is typically 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.
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 the summer and again in the fall. In 2025, they ran the summer sale July 14 - 27, and the fall sale Oct. 27 - Nov. 9. 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 than in previous years.
KCL predicts the next Costco Diaper Sale will happen July 13 - 26, 2026.
Costco never announces this sale in advance, but based on their 2025 pattern, we're predicting the next Kirkland diaper sale will happen July 13 - 26, 2026. The most recent sale ran Oct. 27 - Nov. 9, 2025, and the team at The Krazy Coupon Lady expects Costco to continue their semiannual schedule.
Since this sale only comes around once every six months, it could be worth planning ahead and stocking up when July rolls around. However, keep in mind that the limit is three boxes during the sale.
How do we make our prediction?
Our team at The Krazy Coupon Lady has tracked the Costco diaper sale pattern for years. Here are the most recent sale dates:
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Oct. 27 - Nov. 9, 2025
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July 14 - 27, 2025
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June 3 - 16, 2024
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No sale in November 2024, likely due to the manufacturer switch
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 2025 sales, there was a limit of three boxes per member, and we expect this to continue in 2026.
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.
Best Costco Diaper Deals From the Last Semi-Annual Sale
During the October 2025 Costco Diaper Sale (Oct. 27 - Nov. 9), the discount was $5 - $10 off per box — an improvement from the July sale, which offered $4 off size 1 diapers.
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Kirkland Signature Diapers, Size 1, $9.99 (reg. $14.99) — 33% off
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Kirkland Signature Diapers, Size 2, $14.99 (reg. $19.99) — 25% off
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Kirkland Signature Diapers, Sizes 3 - 6, $29.99 (reg. $39.99) — 25% off
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