Why This Costco Snack Is Constantly Being Returned By Shoppers

Costco gets a lot right. It's brimming with pantry staples and produce in bulk sizes at low prices. Then there's the must-have food court menu, cheap gas, and a host of other lesser-known rewards for card-carrying members. But although the warehouse retailer does so much well, it can't knock everything out of the park. One product in particular has been raking up the negative reviews en masse. That's the Kirkland Signature walnuts, which more than a handful of customers have taken to Reddit to complain about, noting a stale, off taste, a rancid, sour smell, and an almost mushy texture. 

Of note, Costco has peddled a few different walnut options over the years, and offerings could vary based on seasonality and location. Though not all negative reviews (which span a time period over the last three years) make it clear which type they're criticizing, more than one of these Reddit threads is focused on a canned variety of nuts, released under the Kirkland Signature line. These canned walnuts were at least at one time sold in a variety pack box also containing canned pistachio and cashews, but it's consistently the walnuts described by unhappy customers as featuring rancid flavors and a less-than-fresh texture. For what it's worth, the Kirkland 3-pound non-organic bag of walnut halves maintains a solid 4.8-star rating with over 6,000 reviews on Costco's site, but there are 143 one-star reviews for the product, with staleness and rancid flavors a common complaint.

While Costco is notoriously secretive about the growers, manufacturers, and brands it works with, we do know who's behind its walnuts in particular. At least as of 2022, a California-based supplier, Mid Valley Nut Company, was Costco's go-to grower. And we only know this, ironically, due to a recall in 2022 for shelled walnuts which had a — get this — stale flavor and rancid smell.

Now, whether Mid Valley Nut Company was ever the manufacturer behind the canned walnuts some reviewers mention (or still are in 2026) is anyone's guess. Having said that, there's clearly a documented track record of less-than-fresh walnuts from Costco, which fits with the negative reviews.

Certainly, there are countless reasons why loyal Costco shoppers choose its warehouses — regardless of one subpar product. But if nuts are a staple you frequently keep on hand, be wary of the ones you grab from Costco — at least for now. All nuts, but particularly soft varieties with high oil content (like walnuts), are susceptible to spoilage to begin with. And your nose is the best test. A fresh walnut has a pleasant, slightly nutty smell, while a past-its-prime walnut smells almost chemical, like paint or Play-Doh. Our suggestion, regardless of where you purchase from, is to stash nuts in the fridge, or better still the freezer, which can keep those delicious, versatile, and pricey (even if from Costco) little nuggets fresh for up to a year or longer, versus months.