This study aims to develop and validate the Scale for Partnership in Care between staff and families of older adult nursing home (NH) residents—for Family (SPIC-F). The components of partnership were identified on the basis of literature reviews and focus group interviews. The content validity of 41 preliminary items was verified by 10 experts, and a pilot study was conducted. The reliability and validity of the instrument was tested on 330 families of older adult NH residents. The final instrument comprised 20 items in three categories: professional caring and support, cooperative relationship and information sharing, and participation in care. Each item is rated on a four-point Likert scale, with total scores ranging from 20–80. The reliability of the instrument was 0.95, and test–retest ICC was 0.83. This instrument could be utilized to develop interventions to establish an efficient partnership and assess its outcomes.