The extraction of diverse thermolabile but highly value-added chemicals entrapped in the robust cell wall of algal biomass has remained a remarkable challenge. This study investigated the one-pot, simultaneous cell wall disruption and extraction of bioactive astaxanthin from the cysts of Haematococcus pluvialis. During the extraction, wet grinding in the presence of ethanol caused intimate contact of the solvent with the ruptured cells, resulting in almost complete astaxanthin recovery of 31.6 mg/g of dried H. pluvialis (>99% recovery) and a significantly high extraction yield of 46.9 wt % at room temperature (around 22 °C) and atmospheric pressure in a very short time (≤30 min) under a mild milling condition (≤200 rpm). The one-pot method allowed the use of other types of generally recognized as safe solvents such as acetone, ethyl acetate, hexane, and isopropyl alcohol. The antioxidant test indicated that the crude extracts were highly active in scavenging radicals. Thus, our one-pot method was an ecofriendly and economical extraction approach for the complete recovery of astaxanthin in a simple, rapid, low-temperature, and low-pressure manner that minimized the energy required for astaxanthin extraction and suppressed its degradation.