From the YummyYucky team, founded by Nancy Nash

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Swordfish and High-Mercury Fish: Why to Avoid Them

Swordfish and other high-mercury fish are not safe for babies. Mercury builds up in these fish and can harm a baby's developing brain and nervous system, so skip them and choose low-mercury fish like salmon, cod, or trout.

⛔ Avoid swordfish, shark, king mackerel, tilefish, marlin, and bigeye (ahi) tuna.

Mercury is a metal that accumulates in large, long-lived predatory fish, and a baby's brain and nervous system are still developing, which makes them especially sensitive to its effects. For that reason, swordfish, shark, king mackerel, tilefish, marlin, and bigeye (ahi) tuna should not be given to babies or young children.¹ There is no small "safe" amount and no preparation that removes the mercury. If you want to offer fish, and it is a great food to offer, choose a low-mercury option such as salmon, cod, trout, tilapia, or light canned tuna in moderation, cooked fully and checked for bones.

Some foods have rules. YummyYucky remembers them for you. Track what your baby eats and the app flags foods like swordfish and high-mercury fish the moment they come up, watches every new allergen for three days after the first taste, and keeps the whole record dated and pediatrician-ready.

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When to introduce: Avoid for babies and young children
Common allergen?: Yes (fish, a top-9 allergen)
Texture: Not recommended at any texture
Key nutrients: High mercury, not safe for babies

Swordfish, shark, king mackerel, tilefish, marlin, and bigeye (ahi) tuna are high-mercury fish, and they are best avoided for babies and young children entirely. Mercury is a metal that collects in these larger, longer-lived fish, and in a baby it can harm the developing brain and nervous system. Fish itself is a wonderful early food and one of the top-9 allergens worth introducing around 6 months. The fix is to choose a low-mercury one like salmon, cod, or trout rather than skip fish altogether.

Prep School: how to prepare swordfish and high-mercury fish for baby-led weaning (BLW) and purées

🍴 Baby-led weaning

Any ageDo not serve swordfish, shark, king mackerel, tilefish, marlin, or bigeye (ahi) tuna. Mercury cannot be cooked, trimmed, or rinsed away, so these fish stay off the plate for babies and young children.

6 months (low-mercury fish instead)Choose a low-mercury fish like salmon, cod, or trout. Cook it fully until it flakes, check carefully for bones, and offer a soft cooked piece your baby can hold.

9 months+Continue with low-mercury fish in small flaked pieces or soft fish cakes, still checked for bones, with the high-mercury list kept off the plate.

🥄 Purées

6 months (low-mercury fish instead)Choose a low-mercury fish like salmon, cod, or trout. Cook it fully, flake it finely, remove every bone, and mash or mix it into a puree.

9 months+Stir small flaked pieces of low-mercury fish through soft vegetables, or serve them in moist fish cakes, keeping the high-mercury list off the plate.

Is swordfish and high-mercury fish safe? Choking & prep

The core safety issue with these specific fish is mercury, not choking or allergy, and mercury cannot be cooked, trimmed, or rinsed away, so the only safe move is to leave swordfish, shark, king mackerel, tilefish, marlin, and bigeye (ahi) tuna off the plate.¹ When you serve a low-mercury fish instead, cook it fully until it flakes and is opaque throughout, and run a fingertip through it to find and remove every bone, since fish bones are a choking hazard. Skip added salt. Fish is one of the top-9 allergens, so introduce a new low-mercury fish on its own, earlier in the day, and watch for about two hours for hives, swelling, or vomiting, and treat any trouble breathing or swelling of the tongue or throat as an emergency.

Nutrition

Fish in general is a valued source of protein and of the omega-3 fat DHA that supports brain and eye development, which is exactly why the goal is to keep fish on the menu rather than drop it. The catch with swordfish and the other high-mercury fish is that their mercury load outweighs those benefits for a baby, so the nutrition you are after is better delivered by low-mercury choices. Salmon, sardines, trout, and cod offer similar protein and omega-3s without the mercury concern.

Goes well with

Salmon · Cod · Trout · Sardines

Storage & freezing

This is a food to avoid rather than store for your baby, so there are no baby leftovers to keep. If high-mercury fish is being cooked for adults in the house, keep it and its juices separate from your baby's food to avoid mix-ups, and cook any low-mercury fish you are serving the baby fresh and eat it within a day or two kept cold, or freeze it.

More proteins to explore

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Threadfin6 months+

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TilapiaAround 6 months

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TroutAround 6 months

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TunaAround 6 months

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TahiniAround 6 months, thinned or stirred in

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TempehAround 6 months

Introducing this allergen

Common questions

Can babies eat swordfish?

No. Swordfish is one of the high-mercury fish that should be avoided for babies and young children, because mercury can harm a developing brain and nervous system. Choose a low-mercury fish like salmon, cod, or trout instead.

Which fish are too high in mercury for babies?

The ones to avoid are swordfish, shark, king mackerel, tilefish, marlin, orange roughy, and bigeye (ahi) tuna. Mercury builds up most in these large, long-lived predatory fish.

Is a small taste of swordfish okay for my baby?

It is best to avoid it entirely. There is no established safe small amount for babies, and mercury cannot be cooked or rinsed out, so a taste is not worth the risk when good low-mercury fish are easy to serve.

What fish can babies eat instead?

Low-mercury fish are the way to go: salmon, cod, trout, tilapia, sardines, and light canned tuna in moderation. Cook them fully, flake finely, and check very carefully for bones.

Is canned tuna safe for babies?

Light canned tuna is lower in mercury and fine in moderation, but avoid canned white (albacore) tuna and bigeye tuna, which are higher in mercury. When in doubt, salmon or sardines are easy low-mercury swaps.

My baby ate some swordfish at a restaurant, what should I do?

One accidental exposure is not an emergency, since the mercury concern is about regular intake over time. Simply avoid high-mercury fish going forward, and mention it to your pediatrician if you have any concerns.

Sources

FDA/EPA: Advice About Eating Fish

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Last updated September 2026. Next review December 2026. How we write these: built from current published guidance from the AAP, CDC, FDA/EPA, NIAID, WHO, and other pediatric and public-health authorities, with sources cited on the page. See our editorial and medical policy for how we research, source, and update these, and how we double-check the food advice.

This is general information, not medical advice, and is not individualized for your baby. Always talk to your pediatrician about your baby's diet, introducing allergens, and any reaction. In an emergency, contact emergency services.

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