Theory and empirical work suggest that teachers' social capital influences school improvement efforts. Social ties are prerequisite for social capital, yet little causal evidence exists on how malleable factors, such as instructional management approaches, affect teachers' ties. In this cluster-randomized trial, we apply a decision-making perspective to compare a literacy intervention managed under a "fidelity-focused" approach, in which teachers were expected to implement researcher-designed procedures faithfully, versus a "structured adaptive" approach, in which teachers collaboratively planned program adaptations. In the short term, the adaptive approach increased teachers' accessing of intervention-related social capital, but decreased their accessing of social capital unrelated to the intervention. Short-term effects varied based on participants' role in the intervention. No group differences were found on social capital measures one year later, suggesting that the structured adaptive approach did not make teachers more likely to form ties that would be useful outside of the intervention.