There is increasing emphasis on involving the private sector in public health to harness the considerable resources and skills of the business world to address significant health issues. While such collaboration should be encouraged, the involvement of business in public health campaigns can raise unexpected challenges when the approaches and priorities of the public and private sectors clash. We report our experience in developing a public-private partnership to deliver a health promotion intervention using mobile phone text messages in Victoria, Australia. Although the partnership enabled the delivery of text messages on a far wider scale than previously possible, difficulties were experienced during implementation which are likely to have negatively impacted on project outcomes. Our experience has implications for any public health practitioner considering involving a private sector partner in program delivery.