In this paper, we analyzed Darcy‐Forchheimer three‐dimensional bioconvection Casson nanofluid flow due to a rotating disk with entropy generation. The flow is considered with the outcome of thermal radiation and Arrhenius activation energy. For nondimensionality, we utilized the similarity transformations to deal with the problem equations. The homotopy analysis method is applied for the re‐creation of the modeled equations. The biothermal framework is investigated for all the implanted parameters whose impacts are observed through various graphs. There exist intriguing outcomes due to the impacts of various parameters on various distributions. Nanoparticles' concentration diminishes with expansion of the Schmidt parameter and Brownian motion constraint, whereas motile gyrotactic microorganisms' distribution diminishes with expansion of bioconvection Peclet and Lewis numbers. The entropy generation rate increases with the increase of the Brinkman number, Casson fluid parameters, and magnetic parameters. Enrichment in the Reynolds number (Rer) leads to a decrease in the entropy generation rate. Moreover, Bejan number reduces with escalating values of the magnetic parameter, Brinkman number, and Casson fluid parameters. Bejan number (Be) is higher for larger Reynolds numbers and temperature difference parameter.