One of the concerns of parents in the first days of their baby's birth is the baby's risk of jaundice/ hyperbilirubinemia. This is because more than 60% of babies are born with jaundice that, if not timely diagnosed and subsequently treated, can lead to serious damage to their health. On the other hand, despite recent progress in sensor technology for clinical applications, the development of easy-to-use, cost-effective, sensitive, specific, and portable diagnostic devices, which use nontoxic and biodegradable materials in their design and fabrication, is still in high demand. Herein we present an easy-to-use, cost-effective, selective, nontoxic, and disposable photoluminescent nanopaper-based assay kit with a smartphone readout for easy diagnosis of neonatal jaundice through visual determination of Bilirubin (BR) in infants' blood samples. The developed BR assay kit comprises highly photoluminescent carbon dot (CD) sensing probes embedded in a bacterial cellulose (BC) nanopaper substrate (CDBN). The photoluminescence (PL) of the developed BR sensor is quenched in the presence of BR as a PL quencher and then selectively recovered upon blue light (λ = 470 nm) exposure, due to conversion of the unconjugated BR to the colorless oxidation products (non-PL quencher) through BR photoisomerization and photooxidation, that subsequently leads to selective PL enhancement of CDBN. The recovered PL intensity of the developed BR assay kit, which was monitored by integrated smartphone camera, was linearly proportional to the concentration of BR in the range of 2−20 mg dL −1 . The feasibility of real application of the fabricated smartphone-based BR assay kit was also confirmed via comparing the results of our method with a clinical reference method for determination of BR concentration in infant's blood samples. With the advantages of nontoxicity and the extraordinary physicochemical properties of photoluminescent BC nanopaper as the sensing substrate, along with those of smartphone technology, we believe that our developed smartphone-based BR assay kit, as an easy-to-use, cost-effective (∼0.01 Euro per test), portable and novel sensing bioplatform, can be potentially exploited for sensitive, specific, rapid, and easy BR detection and jaundice diagnosis at the point of care (POC) and in routine clinical laboratories as well.