The Astros selected Ullola's contract from Triple-A Sugar Land on Tuesday.
The move adds Ullola to the 40-man roster and protects him from next month's Rule 5 Draft. Ullola spent the entirety of the 2025 campaign at Sugar Land, finishing with a 3.88 ERA and 131:78 K:BB over 113.2 innings. The 23-year-old will compete for an Opening Day roster spot, but a career 15.6 percent walk rate in the minors suggests more seasoning is needed.