Integrated behavioral health (IBH) is an approach to patient care that brings medical and behavioral health providers (BHPs) together to address both behavioral and medical needs within primary care settings. A large, pragmatic, national study aimed to test the effectiveness and measure the implementation costs of an intervention to improve IBH integration within primary care practices (IBH-PC). Assess the time and cost to practices of implementing a comprehensive practice-level intervention designed from the perspective of clinic owners to move behavioral service integration from co-location toward full integration as part of the IBH-PC study. IBH-PC program implementation costs were estimated in a representative sample of 8 practices using standard micro-econometric evaluation of activities outlined in the implementation workbook, including program implementation tasks, remote quality improvement coaching services, educational curricula, and learning community activities, over a 24-month period. The total median cost of implementing the IBH-PC program across all stages was $20,726 (range: $12,381 - $60,427). The median cost of the Planning Stage was $10,258 (range: $4,625 - $14,840), while the median cost of the Implementation Stage was $9,208 (range: $6,017 – 49,993). There were no statistically significant differences in practice or patient characteristics between the 8 selected practices and the larger IBH-PC practice sample (N=34). This study aimed to quantify the relative costs associated with integrating behavioral health into primary care. Although the cost assessment approach did not include all costs (fixed, variable, operational, and opportunity costs), the study aimed to develop a replicable and pragmatic measurement process with flexibility to adapt to emerging developments in each practice environment, providing a reasonable ballpark estimate of costs associated with implementation to help guide future executive decisions.