The visitors had to wait until the closing stages to break Elche's resistance, with second-half substitutes Rodrigo Riquelme and Dani Ceballos playing decisive roles in the victory.
Elche started the encounter with confidence and made life difficult for Manuel Pellegrini's men, who struggled to find their rhythm during the opening exchanges.
Real Betis created some promising opportunities through Pablo Fornals, Isco and Troy Parrott, but Elche goalkeeper Matías Dituro produced important saves to keep the visitors at bay.
Both sides went into the half-time interval with the scoreline goalless.
After the restart, Betis increased their attacking intensity and began creating more dangerous opportunities. However, Dituro continued to frustrate the visitors with several impressive interventions.
Pellegrini's substitutions eventually made the difference.
Rodrigo Riquelme, who had only recently entered the game, broke the deadlock in the 81st minute after José Antonio Morante's header struck the post. Riquelme reacted quickest to the rebound and fired home to give Betis a deserved lead.
The visitors secured all three points in the 89th minute when Marc Bartra rose above the Elche defence to head home Dani Ceballos' corner kick.
Elche were unable to respond, as Real Betis comfortably protected their advantage until the final whistle.
The victory moves Real Betis further into the Champions League qualification conversation, while Elche continue to struggle for positive results on home soil.
Full-time: Elche 0-2 Real Betis
Goalscorers:
• Real Betis: Rodrigo Riquelme 81', Marc Bartra 89'.
Stadium: Estadio Martínez Valero.
Competition: LaLiga, Matchday 12.