The onion, carrots, and celery soften together first, and the kitchen starts smelling like soup before there’s a drop of broth in the pot. I like that this hearty lentil soup with carrots and spinach builds its flavor from ordinary vegetables, then lets the lentils do the work of making the bowl filling.
Brown or green lentils both fit here, and the simmer gives them time to turn tender without losing all their shape. I add the spinach only at the end; it needs just a few minutes to wilt into the hot soup, not a long cook that dulls its color. You end up with a substantial, brothy bowl with tender lentils, soft carrots, and bright ribbons of spinach.
Kitchen Note
I pick through the lentils before rinsing them, rather than tipping them straight into the pot. It takes a moment, and it’s an easy way to catch any small bits that don’t belong in your soup.
Save this hearty lentil soup with carrots and spinach for a cozy, vegetable-packed pot with tender lentils and a fresh handful of greens stirred in at the end.
Why the Carrots and Celery Need Their Own Time Before the Lentils
Lentils are hearty, but they don’t create much sweetness or aroma on their own. Cooking the onion, carrots, and celery in olive oil before adding broth gives those vegetables a chance to soften and develop a rounded base for the soup. Pour in the liquid too early, and the vegetables simmer instead of getting that first stretch of time in the oil.
That order also keeps the finished texture balanced. The carrots need to soften enough to be pleasant on a spoon, while the lentils need a longer simmer to become tender. Giving the vegetables their own turn first means you aren’t waiting for crunchy carrots after the lentils are ready. The garlic and thyme join after the vegetables have softened, so their fragrance has a short moment in the warm oil before the broth goes in.
It’s a simple sequence, but it’s what makes this feel like a developed soup rather than lentils boiled in broth. The tomatoes add a little tang to the earthy lentils, and the spinach comes in only after that base has finished simmering.
How Lentils, Broth, and Spinach Shape This Soup
- Brown or green lentils — Either works in this soup. Brown lentils tend to soften into a more yielding bite, while green lentils generally hold their shape a little more. Pick a single type for a consistent texture, and use dried lentils rather than a pre-cooked substitute for the stated simmer.
- Low-sodium vegetable broth — This is the soup’s main liquid, so a broth you like drinking makes a difference. Low-sodium broth lets the vegetables, tomatoes, thyme, and lentils come through without the saltiness taking over. A standard store-brand carton is fine; the low-sodium choice matters more than buying an expensive one.
- Onion, carrots, and celery — Together, these give the pot its savory, gently sweet base and make each spoonful feel substantial. There’s no need for specialty produce here; fresh, firm everyday vegetables are just right. Slice the carrots evenly so they soften at a similar pace.
- Diced tomatoes, thyme, and bay leaf — The tomatoes bring acidity that balances the lentils, while thyme and bay add a quiet herbal note. Canned diced tomatoes work well, including their juices, so there’s no reason to seek out fresh tomatoes for this pot.
- Baby spinach — Its tender leaves collapse quickly into the hot soup, which is why it goes in after the lentils are cooked. Baby spinach is convenient and needs no chopping; sturdier greens won’t have quite the same quick, delicate finish.
Building the Soup in the Right Order
Soften the Vegetable Base
Heat the olive oil in a 5-quart Dutch oven over medium heat, then add the onion, carrots, and celery. Cook for 6–8 minutes, stirring occasionally, until the vegetables have softened. They shouldn’t be left raw and crunchy, but they don’t need to brown deeply. If the pan looks dry or the onion starts catching, lower the heat slightly.
Give the Garlic and Thyme a Brief Turn
Stir in the minced garlic and dried thyme and cook for 30 seconds, until fragrant. Keep the garlic moving through the vegetables so it doesn’t sit against the hot bottom of the pot. You’ll smell it before the half-minute is up; that’s the cue to move on rather than letting it darken. Burnt garlic can make the whole pot taste bitter.
Simmer the Lentils Until Tender
Add the lentils, vegetable broth, diced tomatoes with their juices, bay leaf, kosher salt, and black pepper. Bring the pot to a boil, then reduce the heat to low, partially cover, and simmer for 30–40 minutes. Check a lentil near the end of the cooking window: it should be tender through, not firm or chalky in the middle. Keep the simmer gentle rather than letting the soup boil hard.
Wilt the Spinach at the Finish
Remove the bay leaf once the lentils are tender, then stir in the baby spinach. Cook for 2–3 minutes, just until the leaves have wilted into the soup. The greens should look soft but still fresh in color. Don’t add them with the lentils at the start; the long simmer would leave them overcooked.
Small Changes That Shift the Pot Without Losing Its Hearty Texture
Choose the lentil texture you prefer
Use brown lentils for a softer, more yielding spoonful or green lentils for lentils that tend to keep their shape a little more. Keep to one variety in the pot so the lentils cook at a similar pace.
Make the pot lower in sodium
The soup already uses low-sodium vegetable broth. For a lower-sodium bowl, leave out the kosher salt; the finished soup will taste less seasoned, but the tomatoes, vegetables, thyme, and lentils still make a satisfying base.
Leave out the spinach for a simpler pot
Skip the baby spinach if you want a more straightforward lentil-and-vegetable soup. The pot will lose the green, tender finish, but the lentils, carrots, celery, and tomatoes still make it hearty. The rest of the cooking method stays the same.
Storage and Reheating
- Refrigerator: Store cooled soup in a covered container for 3–4 days. The lentils absorb some broth as it sits, so the soup will be thicker the next day.
- Freezer: Freeze in airtight containers for up to 3 months. Leave a little room at the top for expansion; the spinach may be softer after thawing, but the soup freezes well.
- Reheating: Warm it in a saucepan over medium-low heat, stirring now and then, until it reaches 165°F. Avoid a hard boil, which can make the lentils break down further.
Questions I Get Asked About This Lentil Soup
Hearty Lentil Soup with Carrots and Spinach
Ingredients
Equipment
Method
- Heat the olive oil in a 5-quart Dutch oven over medium heat.
- Add the onion, carrots, and celery and cook for 6–8 minutes, stirring occasionally, until softened.
- Stir in the garlic and dried thyme and cook for 30 seconds, until fragrant.
- Add the lentils, vegetable broth, tomatoes with their juices, bay leaf, salt, and black pepper, and bring to a boil.
- Reduce the heat to low, partially cover, and simmer for 30–40 minutes, until the lentils are tender.
- Remove the bay leaf.
- Stir in the spinach and cook for 2–3 minutes, until wilted.