Increasing instructional quality in higher education is a key goal of educational development (ED) work, yet demonstrating complex outcomes remains challenging and lacks practical guidance. Evaluating ED services often relies on a reductionist approach characterized by linear assumptions of causal pathways to measure the extent to which instructional outcomes have been achieved and uses proxies such as short-term participant satisfaction. This paper advances a complexity-informed approach for guiding the evaluation of complex outcomes of ED services across individuals and activities within institutions that is adaptable across institutional contexts. To do this, we position the need for innovation in evaluation approaches within current ED literature and practice, and outline key implications of four complexity principles for guiding our approach. Then we describe an iterative process for developing and implementing the evaluation approach within a larger Centre for Teaching and Learning self-study. We describe the transferability of the evaluation approach to contexts beyond the study, and conclude with theoretical, practical, and methodological implications for evidence-based decision-making and strategic planning of ED work.