The world number six, who has not dropped a set so far as he cruised to his fourth final this season, is still seeking his first tour-level title since lifting the trophy in Estoril last April.
The pair were neck and neck in the first set on Barcelona's clay until Ruud took his first chance to break for a 4-2 lead before Etcheverry, seeded 13th, returned the favour in the following game.
The Argentine saved two set points to take it to a tie-break, only to see Ruud clinch it having saved one set point himself after a 76-minute set.
It was just as close in the second but Ruud proved too strong for Etcheverry, playing in his first ATP 500 semi-final.
"Those three finals losses this year have been making me hungrier," Ruud said. "I'm gonna dream about (clinching the title) tonight.
"Last week I put a bit too much pressure on myself. I play my best when I'm cool and don't think too much about it out there. That's what I did today."
Before his defeat by Stefanos Tsitsipas (25) in Monte Carlo last week, Ruud lost finals in Los Cabos and Acapulco earlier this year.
He will face either Tsitsipas or Dusan Lajovic (26) in the final on Sunday.
