Nicknamed Pitbull, Alas came through the youth ranks at Academia La Chelona and joined San Salvador F.C. in 2001.
After sparking interest with his Gold Cup performance, Alas trained with MLS club CD Chivas USA in contemplation of a potential move there. Nothing came of this and he returned to El Salvador. On December 27, 2007, it was announced that Dennis Alas had signed a one-year contract with USL-2 side Real Maryland F.C.[2] On July 14, 2008, Real Maryland F.C. announced that Dennis Alas’ contract had been terminated by mutual consent with the player.[3] The Salvadoran international played a total of 14 games and scored 3 goals and was also selected to the USL-2 team of the week twice including a USL-2 Player of the Week honor for his two-goal performance in the 3-2 win over Cleveland. The Salvadoran was on loan to Real Maryland from his former club San Salvador F.C.
Due to a clause in his contract he became free when the capital club was relegated to El Salvador’s second division. Alas jumped at the chance to join Salvadoran champions C.D. Luís Ángel Firpo.
On the night of June 7, 2007, he scored the game-winning goal against Trinidad and Tobago to give El Salvador their first win of their 2007 Gold Cup campaign. That night, Alas was named by Univision as the Miller Light Player Of The Match.
On September 20, 2013, Alas was one of 14 Salvadoran players banned for life due to their involvement with match fixing.[8]
International goals
Scores and results list El Salvador's goal tally first.