What's actually in Kirkland Signature?
We analyzed Kirkland Signature Adult Chicken, Rice & Vegetable. The first five ingredients are chicken, chicken meal, whole grain brown rice, cracked pearled barley, and chicken fat.
Chicken as the first ingredient means real, named animal protein leads the formula. The second ingredient — chicken meal — is a concentrated protein source that delivers roughly three times the protein of whole chicken by weight. Having both in the top two is a strong protein foundation that most budget brands can't match.
Whole grain brown rice and cracked pearled barley are quality, digestible grains that provide sustained energy and fiber. Chicken fat, preserved with mixed tocopherols (a natural vitamin E-based preservative), rounds out the top five as a highly palatable and nutritious fat source. No corn, no wheat, no soy — at roughly $1 per pound, that's remarkable. Shop on Amazon →
The good stuff
The mineral package is where Kirkland Signature quietly separates itself from most budget competitors. Zinc proteinate, manganese proteinate, and copper proteinate are chelated minerals — meaning they're bound to amino acids for significantly better absorption than the cheap oxide forms found in brands like Purina ONE and Iams. Chelated minerals are a hallmark of premium formulas, and finding them in a $40 bag is genuinely unusual.
Flaxseed meal provides plant-based omega-3 fatty acids for skin and coat health, while fish meal adds marine-based protein and additional omega-3s. Dried chicory root is a prebiotic fiber that feeds beneficial gut bacteria — a functional ingredient that supports digestive health from the inside out. Dried kelp adds trace minerals and iodine for thyroid function.
The value proposition is the headline. A 40-pound bag runs about $40 at Costco — roughly a dollar a pound. That's the same price range as Purina ONE (C/58) and Iams (C/63), brands that score nearly 20 points lower. You're getting B-grade ingredients at a C-grade price, and the only catch is you need a Costco membership to buy it.
The not-so-good stuff
Egg "product" rather than whole eggs is a cost-saving measure. Dried egg product is functional and provides protein, but it's a less premium source than whole eggs or egg powder. It's a minor knock, but it's the kind of ingredient that separates a 78 from an 82.
"Natural flavor" appears as a vague, unspecified ingredient. It's not harmful, but it's not transparent — we'd rather see a named flavor source. Tomato pomace and dried beet pulp are processing by-products used as fiber sources. They're nutritionally fine, but they're filler-adjacent ingredients that take up space on the label.
The Costco-exclusive distribution model is a double-edged sword. It keeps the price low through bulk purchasing power, but it means you can't buy this food at your local pet store, and if your nearest Costco is far away, the convenience factor disappears. Diamond Pet Foods, the manufacturer, has had recall history — most notably a 2012 salmonella issue — though the company has since invested heavily in quality control upgrades.
How it compares
Kirkland Signature's B/78 puts it one point behind Diamond Naturals (B/78), Taste of the Wild (B/78), and Blue Buffalo (B/78) — and the reason is simple. All four are made by the same manufacturer, Diamond Pet Foods, sharing the same supply chain infrastructure that enables quality ingredients at scale pricing. Kirkland Signature is essentially a co-branded Diamond product optimized for Costco's warehouse model.
The value comparison against similarly priced brands is where Kirkland Signature shines brightest. Purina ONE, Iams, and Pedigree all sit in the same price range but score 19 to 59 points lower. Even Purina Pro Plan (C/62), which costs considerably more, doesn't match Kirkland Signature's ingredient quality. If you're already a Costco member, this is one of the best deals in dog food — period.
Read the full breakdowns in our head-to-head comparisons: Kirkland vs Diamond Naturals, Kirkland vs Blue Buffalo, and Redford Naturals vs Kirkland Signature.
Life-stage variant: Kirkland Nature's Domain Puppy (B/79) is the grain-free puppy option with chicken-first protein, salmon oil DHA, supplemental taurine, and a five-strain probiotic blend — manufactured by the same Diamond Pet Foods facility at Costco warehouse pricing.
The bottom line
Kirkland Signature earns a B grade (78/100) from KibbleIQ. Chicken first, chicken meal second, quality grains, chelated minerals, prebiotics, and dual omega-3 sources — all at warehouse pricing that undercuts nearly every competitor in its quality tier. The egg product, vague natural flavor, and Costco-only availability are the only meaningful knocks. If you have a Costco membership and a dog to feed, this is the best dollar-for-dollar value we've found alongside its Diamond Pet Foods siblings. Shop on Amazon →