Heat the olive oil in a large pot over medium heat. Add the onion and cook until it softens.
Stir in the garlic and carrots. Cook for two minutes until the garlic smells fragrant.
Add the potatoes, lentils, diced tomatoes, vegetable broth, Italian seasoning, salt, and black pepper.
Bring the mixture to a boil, then lower the heat to a simmer. Cover the pot and cook for 25 minutes.
Check that the lentils and potatoes are tender. Stir once or twice during cooking to prevent sticking.
Turn off the heat and stir in the fresh parsley before serving.