Montenegro began his career at Paraguayan club Tacuary where he made 51 appearances and scored seven goals before joining Segunda División Uruguay side Deportivo Maldonado.

[2] He joined West Ham on 29 August 2011 where he signed a season-long loan contract saying, "I am very excited to come here and play in England, I am hoping to get a chance to show the fans what I can do.

[citation needed] In July 2014, Montenegro signed with Primera División Paraguaya Club Nacional Asunción to participate in the semi-final stages of the 2014 Copa Libertadores and the Torneo Clasura of the Paraguayan Championship.

[8][9] Replacing injured forward Fredy Bareiro, Montenegro was in the starting line-up of the first-leg of Nacional's semi-final Copa Libertadores fixture against Defensor Sporting on 22 July.

[14] After scoring an impressive 15 goals in 17 league games during the 2016 Primera Division Paraguaya season for Nacional Asuncion, Montenegro was loaned to Cerro Porteño for the remainder of their 2016 Copa Libertadores campaign.