The importance of spirituality in the treatment of mental illness is increasingly acknowledged, but mental healthcare professionals often feel they lack specific competence. An instrument is missing to quantify the spiritual care competence of mental healthcare professionals in the Netherlands. The aim of this study was thus to translate the Spiritual Care Competence Questionnaire (SCCQ) into Dutch and validate it for use in mental healthcare. After translation, the SCCQ-NL was distributed in a cross-sectional design among 3497 healthcare professionals in two mental healthcare institutions (MHIs) in the Netherlands. In the sample of 730 completed questionnaires, exploratory factor analysis revealed seven factors: perception of spiritual needs competencies, team spirit, spiritual self-awareness, documentation competencies, empowerment and proactive opening competencies, knowledge about other religions, and conversation competencies. One item was deleted during the process. Internal consistency for the 25-item SCCQ-NL subscales is sufficient with Cronbach’s alpha ranging from 0.64 to 0.81. Conversation competencies and perception of spiritual needs scored highest in the sample, next to knowledge about other religions and empowerment competencies, while spiritual self-awareness, team spirit and documentation competencies scored the lowest. Small but significant differences in several subscale scores were found for profession, identifying oneself as a believer, practicing prayer and/or meditation, age and working years. The SCCQ-NL can be used for the assessment of spiritual care competencies and for the planning and evaluation of training and improvement strategies.