We report the fabrication and characterization of a surface plasmon resonance (SPR)-based fiber-optic sensor for the detection of low-density lipoprotein (LDL). The probe is prepared by first coating a 50-nm-thick gold film on the unclad portion of the optical fiber core and then immobilizing 4-aminothiophenol (4-ATP), followed by antiapolipoprotein B, over the 4-ATP/Au surface. Spectral interrogation technique is used for the characterization of the probe. SPR spectra are recorded for sample solutions of LDL with concentrations in the range of 0-190 mg/dl. Sensitivity of the sensor is found to be 0.18387 nm per mg/dl. Furthermore, the response time of the sensor is very small (around 2 min). The sensor can be utilized in online monitoring as well. This paper may result in the commercialization of a miniaturized low-cost reusable fast and accurate optical fiber sensor for the detection of LDL level in human blood.