Hormones play major roles in several biological processes. Steroid hormones are crucial for reproductive maturation in women. Abnormal steroid hormones (e.g., estrogen) levels have several pathological conditions, including ovarian failure, bone loss, or increased risk for breast cancer. Thus, accurate and precise detection of steroid hormone levels is crucial for timely health interventions. The current gold standard for steroid hormone detection is immunoassays. Optical measurement technologies are promising alternatives to traditional immunoassays. Optical tools could provide a novel platform for direct, sensitive, and specific measurements of target analytes. Due to their non-photobleaching near-infrared fluorescence, high optical sensitivity, high stability, and sizes within the nanoscale, photoluminescent single-walled carbon nanotubes have great potential for a rapid, sensitive, and specific detection. Here, we investigate an optical biosensor fabricated with SWCNT for hormone detection in biofluids.