[2] Castellanos was awarded a scholarship to study journalism and play football at Florida State University, an experience she describes as life-changing;[2] she spent three college years with the Florida State Seminoles before signing a two-year contract with the Spanish club, Atlético Madrid on 2 January 2020.

[2] She made her Manchester City debut on 18 August 2022, in a 6–0 Champions League win against Kazakhstani side Tomaris-Turan, scoring a penalty in the 89th minute.

On 26 January 2024, Castellanos was acquired by new NWSL expansion franchise Bay FC for a transfer fee.

[7] The next day, Castellanos was acquired by NWSL team Portland Thorns FC and signed to a two-year contract with a club option.

[2] Castellanos started a foundation that encourages gender equality and helps provide football scholarship for South American girls.

[2] She has worked as a studio analyst for NBC and Telemundo at the 2018 (men's) and 2019 (women's) FIFA World Cups,[14] and in Spain.