The most recent guidelines have called for a significant shift towards viral load testing for HIV/AIDS management in developing countries; however point-of-care (POC) CD4 testing still remains an important component of disease staging in multiple developing countries. Advancements in micro/nanotechnologies and consumer electronics have paved the way for mobile healthcare technologies and the development of POC smartphone-based diagnostic assays for disease detection and treatment monitoring. Here, we report a simple, rapid (30 minutes) smartphone-based microfluidic chip for automated CD4 testing using a small volume (30 μL) of whole blood. The smartphone-based device includes an inexpensive (<$5) cell phone accessory and a functionalized disposable microfluidic device. We evaluated the performance of the device using spiked PBS samples and HIV-infected and uninfected whole blood, and compared the microfluidic chip results with the manual analysis and flow cytometry results. Through t-tests, Bland-Altman analyses, and regression tests, we have shown a good agreement between the smartphone-based test and the manual and FACS analysis for CD4 count. The presented technology could have a significant impact on HIV management in developing countries through providing a reliable and inexpensive POC CD4 testing.