Guadalajara Arellano had originally started playing in club Guadalajara's youth ranks around the same time as Javier Hernandez. At the age of 14 he decided to make the move to Club Pachuca where his father Omar Arellano Nuño was offered a job as head coach of Club Pachuca's Juvenil squads. Before returning to Guadalajara in 2007, Arellano had played 394 minutes with
Pachuca and had averaged out one goal every 131 minutes. He scored his first goal for
CD Guadalajara against their town rivals
Atlas, a match that is referred to as "El Clasico Tapatio" (Spanish for "Jalisco's Classic", since they play in the same state and city). On July 12, 2008, while playing the
2008 SuperLiga Arellano scored his second goal with
Guadalajara at the 24th minute with a break-away, suiting the number 9 jersey left behind by
Omar Bravo and his third goal again in the 2008
Superliga against
Houston Dynamo. Arellano scored the two goals that helped Chivas defeat their rivals
Club América in the
Estadio Azteca in the
El Súper Clásico. After a grueling injury that put him in the shelf for months, he returned on February 28, 2009, against F.C. Pachuca where he scored 2 of the 5 goals that his team scored in the 5–0 win. His own father,
Omar Arellano Nuño was assistant and for an even shorter amount of time, manager in 2009. On April 4, 2010, he scored against
America in the
El Súper Clásico and Chivas became the first team in the
Torneo Bicentenario to qualify to the liguilla. He is also not had good luck with injury due that he came back from one. On April 27, 2010, in the
Copa Libertadores, he made an outstanding participation against
Vélez Sársfield where he gave two assist in the 3–0 victory for Chivas de Guadalajara. In a friendly against
FC Barcelona he gave an assist to
Marco Fabian to give
Chivas the lead in their friendly in the
World Football Challenge. Arellano is sponsored by
Adidas and can be seen wearing the
Adidas F50 football cleats.
Monterrey Omar Arellano was traded to C.F. Monterrey for the Clausura 2013 tournament for right back Sergio Perez.
Deportivo Toluca On June 10, 2015
Toluca agreed to sign Arellano on loan with an option of sign permanently. On July 25, Arellano made his official debut for
Toluca defeating
Tigres UANL 0–1, in the opening game for the
2015 Apertura Liga MX, celebrated in the
Estadio Universitario in
Monterrey. ==International career==