This study investigates the performance enhancement of a parabolic trough solar collector (PTSC) through the use of absorber cavities, nanofluids, and increasing the number of absorber tubes. To this end, a laboratory-scale collector was designed and fabricated, featuring three copper absorber tubes, two mirror-finished stainless steel absorber cavities, and a silicon dioxide (SiO₂) nanofluid at three volume concentrations: 0.1%, 0.5%, and 1%. The experiments were conducted under laboratory conditions with a solar irradiance of 900 W/m², inlet and ambient temperatures of 26°C, and a flow rate of 0.24 m³/h over a period of 60 minutes. For all test scenarios, the outlet temperature, useful heat gain, and thermal efficiency were recorded. The results showed that in the baseline configuration — with a single absorber tube and no cavity — the outlet temperature reached 41.8°C, the useful heat gain was 29.18 W, and the thermal efficiency was 36.02%. The simultaneous use of three absorber tubes and an absorber cavity significantly improved the outlet temperature and useful heat gain, reaching 57.3°C and 56.81 W, respectively, with a corresponding thermal efficiency of 70.14%. Furthermore, it was observed that the selected nanofluid had a negligible effect on the thermal performance of the system. The findings of this study can be utilized in the design of efficient large-scale industrial collectors to achieve enhanced thermal efficiency.