In his youth years he played for L.D.U. Quito. Although he came out of the youth ranks of LDUQ, he made no appearances for his team. Liga was not interested with Pita and as a result he was loaned out to Macará.
In the winter transfer window of 2008, Marwin was granted a loanmove to El Nacional. He was used as a substitute during his first days with his new club. However, he became an important player for the club and is now a regular starter being used as a midfielder or a striker. He has been scoring goals for Nacional and is one of the best players of his team.