Background: The Delphi technique is a proven and reliable method to create common definitions and to achieve convergence of opinion. This study aimed to prioritize suicide prevention guideline recommendations and to develop a set of quality indicators (QIs) for suicide prevention in specialist mental healthcare. Methods: This study selected 12 key recommendations from the guideline to modify them into QIs. After feedback from two face-to-face workgroup sessions, 11 recommendations were rephrased and selected to serve as QIs. Next, a Delphi study with the 11 QIs was performed to achieve convergence of opinion among a panel of 90 participants (23 suicide experts, 23 members of patients' advisory boards or experts with experiences in suicidal behavior and 44 mental healthcare professionals). The participants scored the 11 QIs on two selection criteria: relevance (it affects the number of suicides in the institution) and action orientation (institutions or professionals themselves can influence it) using a 5-point Likert scale. Also, data analysts working in mental healthcare institutions (MHIs) rated each QI on feasibility (is it feasible to monitor and extract from existing systems). Consensus was defined as 70% agreement with priority scores of four or five. Results: Out of the 11 recommendations, participants prioritized five recommendations as relevant and action-oriented in optimizing the quality of care for suicide prevention: 1) screening for suicidal thoughts and behavior, 2) safety plan, 3) early follow-up on discharge, 4) continuity of care and 5) involving family or significant others. Only one of the 11 recommendations early follow-up on discharge reached consensus on all three selection criteria (relevance, action orientation, and feasibility). Conclusions: The prioritization of relevant and action-oriented suicide prevention guideline recommendations is an important step towards the improvement of quality of care in specialist mental healthcare.