Asparagus
Basil grows well paired with asparagus.
Basil and asparagus attract beneficial insects (e.g., ladybugs), which helps control the presence of aphids and other pests in the garden.
Basil repels flies and mosquitoes, reducing the need for chemical pesticides.
Basil repels the asparagus beetle, which feeds on the tender tips of new asparagus shoots. In turn, asparagus shelters basil from strong winds.

Beets
The leafy green tops of beets benefit from the pest-repelling aromas of nearby basil plants.
Basil is a companion that can improve the growth and flavor of your beets.

Borage
Borage is a good companion plant for Basil because it attracts pollinators, such as bees and other beneficial insects, to the garden.
Borage may also draw out essential minerals from the soil that may be utilized by your Basil to enhance its development and vigor.
Borage helps your Basil grow and taste better.

Broccoli
Basil attracts beneficial insects to your broccoli plant but also prevents aphids from attacking your broccoli. Basil also keeps white flies, hornworms, and beetles away from other plants.

Cauliflower
Basil attracts beneficial insects to your cauliflower plant but also prevents aphids from attacking your cauliflower. Basil also keeps white flies, hornworms, and beetles away from other plants.

Chamomile
Chamomile makes a good companion to Basil in the herb garden because its presence increases the amount of essential oil that Basil produces.
This enhances the flavor of your Basil in culinary preparations and increases its skills as a pest-repellent in the garden.

Chives

Chives enhance the flavor of your Basil.
Chives help increase essential oil content in neighboring plants and make Basil more potent as a pest repellent.
In addition, the scent of chives can help repel aphids and other pests from your basil plants.

Garlic
Both basil and garlic aid in the prevention of spider mites, aphids, and whiteflies, resulting in a healthier garden patch and better harvests.
Basil and garlic are said to enhance one another’s flavors when grown together.
Garlic can also keep away squirrels and rabbits.

Grapes
Basil can repel bad insects away from your grapes.

Marigolds
Basil and marigolds make great companion plants because they benefit from each other’s qualities.
Basil and marigolds naturally repel pests. When planted in tandem, they emit a strong smell that deters garden pests such as aphids, beetles, and nematodes.
Pairing basil with marigolds can also prevent slugs and snails from harming your Basil.

Nasturtium
Nasturtium is a good companion plant for Basil because it acts as a trap crop.
Nasturtium traps pests such as aphids away from your Basil.
In addition, Nasturtiums add cheerful color to the garden, and their flowers are edible.

Oregano
Oregano enhances the flavor of your Basil.
Oregano helps increase essential oil content in neighboring plants and makes Basil more potent as a pest repellent.
When oregano is in bloom, it might draw beneficial insects.

Parsley
Basil and parsley are great companion plants. They share similar growing requirements.
Both need full sun, well-draining soil, and consistent moisture.
Basil and parsley are more effective when planted together as companions for other plants, like asparagus and brassicas.

Peppers
Basil grows well when paired with bell peppers and chili peppers.
Basil improves the growth and flavor of peppers.
Basil aids in deterring several common garden pests, such as aphids, spider mites, thrips, mosquitoes, and flies that are often attracted to peppers.

Petunias
Petunias are a great companion plant for the herb garden.
Petunias repel many annoying pests, including asparagus beetles, leafhoppers, aphids, and tomato worms.
Petunias also offer cheerful colors to your herb or vegetable garden.

Potatoes
Basil improves the flavor of peppers.
Basil aids in deterring several common garden pests, such as aphids or potato beetles.
Basil is thought to promote a stronger root system in potatoes.

Radishes
Radishes can be used as row markers – they mark out the row where your Basil has been sown.
Radishes are a good companion plant for Basil because they benefit from the pest-repelling aromas of nearby basil plants.

Tomatoes
Basil improves the growth and flavor of tomatoes.
Basil helps tomatoes to overcome insects and diseases.
Basil repels flies, mosquitoes, aphids, whiteflies, and tomato hornworms, reducing the need for chemical pesticides.
Basil attracts bees, butterflies, beneficial insects, and pollinators, improving pollination.

Cucumbers
Aromatic herbs, like Basil, can affect the taste of your cucumber

Sage
Sage and other aromatic herbs can stunt the growth of your cucumbers.

Rue
Rue should also be kept away from Basil. 
Basil and rue dislike each other. Perhaps this is because Basil is sweet and rue is very bitter.

Fennel
Fennel is one of the few plants that has mostly bad companions. Most plants dislike Fennel, and it should be planted well away from the vegetable garden. Fennel inhibits the growth of any nearby plant, including Basil.

Thyme
Although thyme is an aromatic herb like Basil, Thyme and Basil do not share the same growing requirements. Thyme prefers drier and sandier soils, while Basil prefers more moist soils.