in january 2015, it was announced that banini had signed with the washington spirit for the third season of the national women's soccer league (nwsl). of her signing, spirit head coach mark parsons said, "estefania is an exceptional talent and i do not think there is a player like her in the league. she is going to give the team a very different dynamic and provide us with real quality in the final third." she played and started in the first four games of the 2015 season before sustaining an injury which sidelined her for the rest of the year. banini came back strong midway through the 2016 season, scoring five goals in a seven-game period before sustaining another injury. the argentine was awarded the spirit 2016 golden boot award, nwsl goal of the week for week 13, nwsl player of the week for week 13, and nwsl player of the month for july.