Slow cooker lentil soup is supercharged with nutrition! Truly a prep-and-go recipe, it’s easy to throw together and make extra for hearty, filling meals throughout the week. Customize with additional protein and veggies, or spice it up even more – the choice is yours!

bowl of slow cooker lentil soup in front of slow cooker

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What’s To Love About This Recipe

Slow cooker lentil soup is hearty and wholesome. You can rest assured you’re eating a great meal full of plant-based protein and fiber.
This type of recipe is the best kind for slow-cooking – it’s truly a set-it-and-forget-it soup! Try out this perfect option for busy days.
Not only is this a budget-friendly recipe made with pantry staples, but it’s also very freezer-friendly. This is a great meal prep recipe because of the many ways to keep the ingredients on hand and store the leftovers.
You can customize the flavors with add-ins or toppings. Make it just how you like! Plus, it’s easy to make it completely vegetarian by using vegetable broth.
A bowl of lentil soup is comforting and flavorful without being too heavy. Serve this up with a sandwich or salad for a tasty, filling meal!

Ingredients Needed

Green lentils – Lentils are an often underrated source of incredible nutrition. They are full of protein and fiber and have a distinct flavor that works well with savory herbs and veggies. Green lentils also have a thicker skin that stays intact during cooking.
Yellow onion – Diced yellow onion adds a bit of sweetness to the soup.
Carrots – Carrots are another excellent nutritional addition! Peel and chop medium carrots to add texture and flavor.
Garlic – Fresh garlic really deepens the aroma of the soup.
Garlic and Herb Seasoning – I love my homemade blend, but you can also use your preferred brand. This seasoning is an excellent base, and you can add more salt or spice as desired.
Smoked paprika – This hint of smokiness deepens the overall flavor.
Red pepper flakes – Get a bit of spice with a pinch of red pepper flakes. It’s just enough to add complexity, and you can always increase the heat if you like.
Salt – Balance everything out with a bit more salt.
Crushed tomatoes – Crushed tomatoes add a rich element to the soup base and thicken it up. The hint of acidity also balances the other deeper flavors.
Chicken or vegetable broth – Use either broth based on your preference. The broth will infuse a savory taste into the lentils during cooking.
Fresh spinach – Add this at the end of cooking to wilt it and preserve some of the freshness. This is an excellent, nutrient-dense addition that provides a great contrast of texture and color.
Olive oil – A bit of olive oil, added at the end of cooking, creates a smooth, flavorful finish before serving.

Ingredients to make lentil soup all laid out and pre-portioned on counter

How To Make Slow Cooker Lentil Soup

Add all ingredients except spinach and olive oil to the slow cooker.

Lentil Soup all ingredients in slow cooker

Cover and cook on low for 6-8 hours or high for 3-4 hours until the lentils are softened.
Stir in spinach and olive oil and heat through for an additional 15 minutes.

Spinach laid on lentil soup in slow cooker

Serve garnished with chopped herbs, shaved parmesan, a dollop of Greek yogurt, or as desired.

completed lentil soup in the slow cooker

Pro Tips

The best lentils to use for this soup are either green or brown lentils. Green lentils hold their shape well and are ideal for hearty soups, and brown lentils also work well and have a slightly softer texture. Avoid red lentils since they break down too quickly and are better for pureed soups.
If the lentils are still hard after cooking, they may need more time. Try cooking on high for an extra 30-60 minutes. Also, make sure the broth covers the lentils fully and add more if needed.
No need to soak or cook the lentils beforehand! Just rinse and add straight to the slow cooker.
Don’t leave the soup on the “keep warm” setting for long periods since it can overcook the lentils and make them mushy.

Recipe Substitutions and Variations

Green, brown, or French lentils all work. Try a combination for variance in texture and color.
Make a heartier lentil soup by adding extra protein. Stir in cooked bacon crumbles, sausage, diced ham, or shredded rotisserie chicken near the end of cooking.
Extra veggies can really up the nutrition of this soup! Chopped zucchini, bell peppers, sweet potatoes, celery, or mushrooms can be added with the lentils.
Another veggie option is to stir in frozen peas or corn at the end for extra texture and color.
Spice up the soup by adding cumin, curry powder, or a dash of hot sauce.
To make this soup fully vegetarian, be sure to use vegetable broth instead of chicken broth.

close up of wooden spoon with a scoop of lentil soup

Alternative Cooking Methods

Stovetop:

In a large pot, sauté onions, carrots, and garlic in olive oil. Add the remaining ingredients – except spinach and extra olive oil.
Simmer for 30-40 minutes until the lentils are tender. Stir in spinach and olive oil just before serving.

Instant Pot:

Add all ingredients (except spinach and olive oil) to the pot and cook on high pressure for 15 minutes.
Allow a natural release for 10 minutes. Stir in spinach and olive oil after cooking, then serve.

What To Serve With Slow Cooker Lentil Soup

Toppings

Customize your lentil soup with a variety of toppings. Add a sprinkle of fresh-chopped herbs, shaved parmesan, a dollop of Greek yogurt, an extra drizzle of olive oil, or crushed red pepper flakes.

Sides

Serve a bowl of soup with crusty bread, Buttermilk Drop Biscuits, a simple grilled cheese sandwich, or garlic toast. Add a side salad for a crunchy-fresh component and enjoy!

Freezer Meal, Storage, and Reheating

Freezer Meal Instructions:

Add all ingredients (except spinach and oil) to a freezer-safe bag.
Lay the bag of soup flat to freeze. When ready to cook, thaw in the fridge overnight and dump it into the slow cooker.
Add spinach and oil at the end as usual.

How to Best Store Leftovers

Fridge:

Store leftover lentil soup in an airtight container in the fridge for up to 4 days. The flavors will continue to deepen, which makes this a perfect soup to meal prep!

Freezer:

This soup also freezes well for up to 3 months. Use Souper Cubes to easily portion out servings to defrost for a quick meal when you need it.

How to Best Reheat Leftovers

Lentil soup will thicken slightly when stored, as the lentils expand and soak up the liquid. When reheating, it is helpful to add a splash of broth to prevent the soup from thickening too much.

Warm leftovers gently over medium heat on the stovetop or heat in short bursts in the microwave, stirring in between.