This article describes the development and testing of the Family Nursing Practice Scale (FNPS). This self-report questionnaire is designed to measure perceived changes in family nursing practice including attitudes toward working with families, critical appraisal of their family nursing practice and reciprocity in the nurse-family relationship. Categories were derived from a needs assessment, competence as effective application of knowledge and skill and theoretical foundations for family assessment and intervention. Psychometric testing (content, construct validity, internal consistency, and test-retest reliability) was undertaken with 140 psychiatric nurses in Hong Kong. Practice appraisal and nurse-family relationships accounted for 56.4% of the variance. Cronbach's alpha reliability coefficients were .88 and .73 for the two subscales, respectively, and .86 for the scale overall. Test-retest reliability ranged from .62 to .93 on the individual items. The results provide preliminary evidence of the reliability and validity of the FNPS. The instrument provides quantitative and qualitative evaluation components.