Kenya Water Services Regulatory Board (WASREB) Impact Report indicates a stagnation in water coverage at 55 percent, for the last three years, contrary to the 2015 target of 80 percent. One main reason for the stagnation is weak cross-county cooperation between hydrologically interdependent governments. WASREB has little guidance on what indicators to use to enhance cross-county water cooperation. Through literature review, we assess whether the UN-Water methodology for assessing Sustainable Development Goals (SDG) 6.5.2 would provide useful guidelines. Based on the literature review outcomes, we design a water policy game known as Nzoia WeShareIt. After that, we play seven-game sessions in four county governments (Busia, Bungoma, Kakamega, and Trans Nzoia), on 11–22 July 2016. We use the in-game and post-game questionnaire data to measure learning outcomes on interdependence and cooperation. The findings indicate that Nzoia WeShareIt policy game as a form of experiential learning increased understanding on the value of cross-county cooperation. The study constitutes a practical guideline to WASREB and a quick reference tool to be explored when designing indicators to monitor cross-county cooperation. We also propose a mixed method approach that incorporates team interdependence indicators as distinct and separate indicators from cooperation. Moreover, we recommend strengthening SDG 6.5.2 indicator to measure transboundary water cooperation inputs, processes and outcomes.