Community-based HIV testing and counseling (HTC) programs have become an important part of the healthcare system in South Africa and other low- and middle-income countries with a high HIV prevalence and strained primary healthcare system. Current HTC programs excel at identifying people living with HIV (PLH) but leave gaps in linkage to care and antiretroviral therapy (ART) as most HTC programs do not have the capacity to ensure that linkage has occurred. This article presents the protocol for an mHealth study, that is, pilot testing a mobile platform in KwaZulu-Natal (KZN), South Africa, to improve linkage to care and ART adherence after home-based HTC. Testing data are shared with designated clinics. PLH are identified using fingerprint scans, mobile numbers, or South African IDs. If PLH do not present at a designated clinic after testing HIV positive, study field staff are sent SMS alerts to prompt follow-up visits. Similarly, if PLH do not refill ART prescriptions after their initial 1-month dose runs out, SMS alerts that are sent to field staff. This paper presents the mHealth study protocol and baseline sample characteristics (N = 101 PLH). Analyses will summarize rates of linkage to care and ART prescription refills. Cost-effectiveness analyses will examine the costs and benefits of linkage and ART adherence using our mHealth system. Linkage to care rates will be compared between our study and a historical control, that is, provided by a prior HTC program that was conducted in KZN without our mHealth system (n = 615).