Slow Cooker Lentil and Sweet Potato Soup

Ingredients

• 1 cup dry brown or green lentils, sorted and rinsed
• 1 pound sweet potatoes, peeled and cut into 1/2-inch cubes
• 2 medium carrots, cut into 1/2-inch pieces
• 2 celery ribs, chopped
• 1 small onion, diced
• 3 garlic cloves, minced
• 6 cups low-sodium vegetable broth
• 1 teaspoon ground cumin
• 1 teaspoon dried thyme
• 1/2 teaspoon smoked paprika
• 1/4 teaspoon black pepper
• 3 cups fresh baby spinach
• 1 tablespoon lemon juice, plus more to taste
• Salt to taste

Preparation and cooking

1. Sort lentils on a tray, discard debris, and rinse in a fine-mesh strainer. Wash produce before cutting.
2. Add lentils, sweet potatoes, carrots, celery, onion, garlic, broth, cumin, thyme, paprika, and pepper to a 5- to 6-quart slow cooker. Follow the manufacturer’s fill limits.
3. Cover and cook on Low for approximately 6–8 hours or High for 3–4 hours. Begin checking at the early end; lentils should be fully tender and sweet potato cubes easily pierced with a fork. Continue cooking if either is firm.
4. Stir in fresh spinach, cover, and cook about 10 minutes until wilted. Add lemon juice after lentils soften, then taste and adjust salt.

Brown or green lentils hold their shape better than red split lentils. No soaking is required. Do not substitute dried kidney beans; they need a separate safe preparation process. Keep lemon and other acidic additions until the lentils are tender.

Get the texture you want

For a thicker soup, mash a few sweet potato cubes into the broth. For a thinner soup, stir in small amounts of hot broth. Small, even vegetable pieces help the roots and lentils finish together. Older lentils may take longer to soften. Keep the lid on between checks.

Serving and meal preparation

Serve with toast or a side salad. Portion a few lunches only after following the cooling steps below. Organize ingredients with our mise en place guide, and use the onion-dicing instructions for even pieces.

Safe serving, storage, and reheating

Use Low or High to cook, never Warm. Once cooked, keep soup at 140°F or hotter if holding for service. Divide leftovers into shallow containers and refrigerate promptly, within two hours (one hour above 90°F). Keep the refrigerator at 40°F or below. Use refrigerated soup within 3–4 days; freeze portions for up to about 3 months for best quality.

Reheat in a saucepan or microwave to at least 165°F throughout; bring soup to a rolling boil on the stove while stirring. Add broth if needed. A slow cooker is for holding already-hot leftovers, not reheating chilled soup. Read our complete leftovers guide.

Safety sources

Guidance checked October 12, 2026: USDA slow-cooker safety and USDA leftovers guidance.