Oscar Diaz was a recurring character in the second season. He was portrayed by Andres Londono.
Oscar is from the United States and is the brother of Andres. Before the outbreak, he and his family planned a wedding to celebrate his marriage with Jessica at the Rosarito Beach Hotel in Baja California, Mexico.
Oscar was in Rosarito with his family celebrating his wedding at the hotel. The wedding celebrations continued despite the rumors of the outbreak threatening to close the border. As the guests enjoyed the party, Oscar and his wife Jessica proceed to the dancefloor. Jessica's parents debate whether they should leave Mexico. After the dance, Jessica's father Charles is called to the dance floor for the father-daughter dance. However, during the dance Charles suffered a heart attack and reanimated, taking a bite out of Jessica's cheek as she tried to perform CPR. As panic ensued in the ballroom, Elena Reyes locks everyone inside in an effort to contain the situation.
A month later, it is revealed that Oscar survived ballroom incident with his mother-in-law Ilene, his brother Andrés, and several other wedding guests. He and the others corner Elena and Alicia outside the bar in order to get the master keys to the hotel. They are successful in retrieving the keys, but are attacked by zombies released from the bar by Alicia.
Oscar is later seen on his balcony as Madison attempts to negotiate with the wedding guests. He listens to Madison as she tries to convince his group that everyone needs to work together in order to secure the hotel and survive. Later, as the survivors lure the zombies out of the hotel, he watches from his balcony with Ilene. That night, as the survivors have a dinner to celebrate their new unity, he is on the 17th floor outside the honeymoon suite, standing guard. He refuses to let his undead wife, who is behind held inside the room, to be put down. However, Strand and Oscar have a talk about love and is convinced to allow Strand to put Jessica down.
In "Wrath", when Travis Manawa locks himself in a room with Brandon and Derek and begins to brutally beat them over Brandon's shooting of Chris, Oscar grabs the keys to the door and peeks his head inside. However, a full of rage Travis forcefully slams the door on his head to keep everyone out, knocking Oscar out cold.
In "North", Andres Diaz attempts surgery on Oscar to reduce the swelling on his brain but is unable to stop the swelling and bleeding as Oscar succumbs to his injuries. Andres and Hector then attempt to get revenge by killing Travis but Alicia intervenes.