This paper focuses on a new approach for facilitating the participation of stakeholders in a process of strategic planning known as open strategic planning (OSP). OSP is recognised through three characteristics: inclusiveness, transparency, and the use of information technology (IT) tools. Drawing on the theoretical foundations of OSP, the research explores moderating factors impacting the relationship between these characteristics and OSP effectiveness by referring to qualitative data obtained from two open strategic planning projects. A secondary aim was to examine how stakeholders interpret the effectiveness of OSP in an organisational setting. Results indicate various moderating factors (level of trust, IT literacy, and diversity of participants) impacted the relationship between the characteristics of OSP and strategic planning effectiveness. The study formulates eight propositions, each is discussed in relation to the existing literature on strategic planning effectiveness. This paper is significant as it is the first exploratory research linking openness and strategic planning outcomes.