Despite documented health benefits of household water treatment and storage (HWTS), achieving sustained use remains challenging. In prior evaluations of a long-term HWTS program in Haiti, multiple marketing interventions failed to increase use or had prohibitively high costs. Using mobile phones is a potentially cost-effective way to change HWTS behavior. We conducted a randomized experiment to evaluate the impact of sending short-message service (SMS) messages to promote household chlorination in this program in Haiti. Households (n = 1327) were randomly assigned to: One of four SMS frequencies; one of ten behavioral constructs; “cholera” or “disease” framing; and one or zero household visits from a sales agent. During the three-month campaign, there were no statistically significant relationships between the four outcomes related to chlorine purchases and any SMS frequency, any behavioral construct, or either “cholera” or “disease” framing. Receiving one visit increased the probability of purchasing a bottle of chlorine by 17.1 percentage points (p < 0.001) but did not affect subsequent purchase behavior. Costs of managing the SMS campaign were higher than expected. SMS campaigns may not be cost-effective behavior change interventions in certain contexts. If pursued, we recommend simple interventions, timed with the target behavior, and tailored to mobile phone usage patterns of the target population.