In order to probe how social movement messages foster participant mobilization, this study utilized an experimental design to investigate collective action frames, core messaging tasks that define problems, assign blame, convey a plan of action, and inspire participation. The study compared the effects of climate change messages that contain motivational frames with those that do not, incorporating the influence of resonance, and exposure to competing and counter frames. Results revealed that motivational frames contributed to mobilization, especially intention to act, under conditions of resonance and with exposure to counter frames. Salience primed participants to respond to motivational frames, however for some, motivational frames decreased intention to act. As social movements and climate change continue to profoundly shape our world in myriad ways, we will be better prepared to address those changes with information provided here.