OBJECTIVES: To develop a reliable, valid self-report questionnaire assessing the impact of caregiving on work performance and productivity among informal caregivers of individuals with schizophrenia, many of whom need and/or want to work.   METHODS: The Caregiver Work Limitations Questionnaire (CWLQ) is based on the WLQ, a validated measure of the burden of health problems on work performance and productivity. The CWLQ was administered to the employed segment of a large community-based caregiver sample. Using published standards to evaluate the CWLQ’s psychometric performance, the analysis addressed distributional properties (e.g., floor and ceiling effects and missing responses) and tested its hypothesized four-scale structure (e.g., item-to-total scale correlation, internal scale homogeneity tests, exploratory factor analysis [EFA] and confirmatory factor analysis [CFA]). Construct validity tests using Pearson r correlation hypothesized higher scores with more frequent caregiving and lower social support. A random subsample of 50 employed caregivers was required for a test/re-test. Pearson r correlation summarized test/re-test results. RESULTS: In a total sample of 1,142 caregivers, 62% (n=710) were employed. Their CWLQ scale scores indicated that they were limited in their work performance in the past two weeks between 22.0 and 29.5% of the time on average (SDs 23.2-23.1, respectively). Mean at-work productivity loss was 7.7% (SD 5.3%).  The missing CWLQ item rate was 9%. Item to total correlations, discrimination tests and homogeneity tests and CFA all confirmed the hypothesized scales. In construct validity tests, the scales and summary score demonstrated the hypothesized relationships (p ≤ .001 on 10/12 tests). Test/re-test scale correlations were 0.58 to 0.82 (p<0.001).  CONCLUSIONS: During the adult life course, many caregivers of individuals with severe and chronic mental disorders will need and/or want to work but face significant challenges doing so. The CWLQ is a reliable and valid tool for assessing this dimension of caregiver activity and cost.