Objectives: Many studies have examined quality effects of nursing facility (NF) staffing, but few have examined effects of unionization. Concerned with possible effects of unionization on quality, we analyzed unionization and local market climate of unionization, predicting both complaints (reflecting either quality problems or better monitoring and advocacy) and the substantiation of serious complaints (indicating major quality problems). Method: Data were analyzed on California freestanding NFs in 1999 (N= 1,155). OLS regression was employed to predict both quality complaints and serious violations, the latter both controlling and not controlling for numbers of complaints. Results: Unionized NFs showed more complaints than did nonunionized NFs. Nonunionized NFs had more serious violations, particularly when the proportion of other county facilities unionized was higher. Discussion: These findings suggest that unionization enhances problem reporting while, especially in stronger union environments, reducing the incidence of serious quality violations.