The present study deals with the experimental performance of a Marquise shaped channel solar flat-plate collector using Al 2 O 3 /water nanofluid and base fluid (pure water). The experimental setup comprises a special type of solar flat plate collector, closed working fluid systems, and the measurement devices. The absorber plate is made of two aluminum plates sandwiched together with Marquise-shaped flow channels. The volume fraction of 0.1% of Al 2 O 3 /water nanofluid is used for this study. The various parameters used to investigate performance of the collector energy and exergy efficiency are collector inlet and outlet fluid temperatures, mass flow rate of the fluid, solar radiation, and ambient temperature. The flow rate of nanofluid and water varies from 1 to 5 lpm. The maximum energy efficiencies attained are 83.17% and 59.72%, whereas the maximum exergy efficiencies obtained are 18.73% and 12.29% for the 20 nm—Al 2 O 3 /water nanofluids and pure water, respectively, at the flow rate of 3 lpm. These higher efficiencies may be due to the use of nanofluids and the sophisticated design of the absorber plate with the Marquise shaped channel.