The move was made before Thursday night's game against the New York Yankees.
Betancourt hurt the ankle toward the end of spring training, but still managed to play in 15 of the Royals' first 23 games. He was hitting .280 with a homer and three RBIs.
Falu has spent parts of 10 seasons in the minors and was in his fourth straight year at Omaha, where he was hitting .306 with a homer and 10 RBIs. He's never played in the majors.
To make room on the 40-man roster, the Royals transferred closer Joakim Soria to the 60-day DL. He's out for the season after having Tommy John surgery.