This chapter analyses the Ocean Acidification Alliance (OAA) against five elements of global experimentalist governance. The OAA, launched in 2016 by Pacific Coast governments, comprises over 145 members addressing ocean acidification. Evaluating the five elements reveals: (1) A shared problem exists – members agree on OA definition and causes; (2) Open-ended goals are present – six framework objectives like ‘reduce CO2 emissions’ with provisional, loosely worded targets; (3) Delegation occurs – members create Action Plans with discretion to experiment, although delegation is not solely to lower levels; (4) Feedback and peer review are limited – information sharing occurs through webinars and meetings but lacks systematic reporting on specific metrics; (5) Goal adjustment is possible – goals and metrics can evolve based on scientific findings and member experiences. A key limitation is that metrics lack specificity, undermining systematic reporting and peer-review cycles essential to experimentalist governance. No penalty default exists due to voluntary membership. While the OAA exhibits features of experimentalist governance, the absence of concrete metrics weakens the recursive learning process. Future metric development could enhance the implementation of experimentalist governance within this voluntary, multilevel climate coalition.