This paper studies whether government-issued skill certification improves labor market integration when workers' skills are hard to verify. We evaluate a randomized offer of access to an occupation-specific certification program in Colombia among locals and migrants, two groups with different ex ante signaling capacity. The program certifies existing skills rather than providing training. Among locals, the offer increases employment by reducing inactivity and raises hours worked. The effects persist unevenly over time and are robust to attrition bounds and alternative outcome measures. Among migrants, estimates are less precise and provide no evidence of effects in employment, hours, or wages. The results show that a common skill certification generates different patterns of labor-market adjustment among locals and migrants.