Recipients of welfare benefits have elevated rates of mental health and substance-related problems relative to the general public; however, low acculturation among Latinos may be a protective factor for both conditions. Lower acculturation among Latinos is associated with lower levels of mental health and substance-related problems relative to highly acculturated individuals. To our knowledge, there are few published studies examining the potential protective effects of low acculturation, defined herein as Spanish language preference, among Latina participants in welfare programs. Screening and treatment of mental health and substance-related problems in this population are important because work requirements for benefits receipt have been implemented and mental health or substance-related problems may be barriers to meeting these requirements. This analysis assesses the prevalence of mental health and substance-related problems among female participants in California's response to 1990s federal welfare reform legislation--the California Work Opportunity and Responsibility to Kids (CalWORKs). Although mental health needs may be similar among CalWORKs recipients regardless of acculturation, substance-related problems may be less frequent among Spanish-speaking Latinas participating in the CalWORKs program. Low acculturation was not a significant predictor of mental health need but had a protective effect with regard to substance-problem risk after controlling for several other substance-problem risk variables.