Cook spaghetti according to package instructions until al dente. Drain and set aside.

In a skillet, brown the ground beef over medium heat until fully cooked. Drain excess fat.

Add marinara sauce and taco seasoning to the skillet. Stir to combine and simmer for 5 minutes.

Mix the cooked spaghetti into the beef and sauce mixture until well combined.

Preheat the oven to 350°F (175°C) if warming taco shells.

Fill each taco shell with the spaghetti mixture.

Top with shredded lettuce, diced tomatoes, shredded cheese, sour cream, and jalapeños as desired.

Serve immediately and enjoy your spaghetti tacos!