The World Health Organization now recommends parasitological confirmation for malaria case management. Rapid diagnostic tests (RDTs) for malaria are an accurate and simple diagnostic to confirm parasite presence in blood. However, where they have been deployed, adherence to RDT results has been poor, especially when the test result is negative. Few studies have examined adherence to RDTs distributed or purchased through the private sector. The Rapid Examination of Malaria and Evaluation of Diagnostic Information (REMEDI) study assessed the acceptability of and adherence to RDT results for patients seeking care from private sector drug retailers in two cities in Oyo State in south-west Nigeria. In total, 465 adult participants were enrolled upon exit from a participating drug shop having purchased anti-malaria drugs for themselves. Participants were given a free RDT and the appropriate treatment advice based on their RDT result. Short Message Service (SMS) text messages reiterating the treatment advice were sent to a randomly selected half of the participants one day after being tested. Participants were contacted via phone four days after the RDT was conducted to assess adherence to the RDT information and treatment advice. Adherence to RDT results was 14.3 percentage points (P-val <0.001) higher in the treatment group who were sent the SMS. The higher adherence in the treatment group was robust to several specification tests and the estimated difference in adherence ranged from 9.7 to 16.1 percentage points. Further, the higher adherence to the treatment advice was specific to the treatment advice for anti-malarial drugs and not other drugs purchased to treat malaria symptoms in the RDT-negative participants who bought both anti-malarial and symptom drugs. There was no difference in adherence for the RDT-positive participants who were sent the SMS. SMS text messages substantially increased adherence to RDT results for patients seeking care for malaria from privately owned drug retailers in Nigeria and may be a simple and cost-effective means for boosting adherence to RDT results if and when RDTs are introduced as a commercial retail product.