Fill a cocktail shaker halfway with ice.
Pour in tequila, mango juice, lime juice, jalapeño simple syrup, and Cointreau.
Shake well until the shaker feels cold to the touch.
Run a lime wedge around the rim of your glass and dip it in Tajin or salt for a zesty kick.
Fill the glass with fresh ice and strain the margarita over the top.
Garnish with mango slices, jalapeño, lime, or mint. Serve immediately and enjoy!