This study aimed to screen different solvents (ethanol, ethyl acetate, and n-hexane) of Coelarthrum muelleri for secondary metabolites and subject them to physicochemical analysis, including ash, swelling index, pH, and color tests with different reagents. Seaweeds have been recognized in the pharmaceutical industry for their broad spectrum of structural diversity and wide range of pharmacological activities for health and disease management. Coelarthrum muelleri from red algae was taken as a sample for this study. It was collected from the coastal range of Buleji and Kakapir beaches in Karachi, Pakistan. Three extracts of Coelarthrum muelleri (ethanol, ethyl acetate, and n-hexane), depending on their polarity, were subjected to phycochemicals of ten chemical compounds (glycosides, quinones, phenols, coumarins, steroids, alkaloids, saponins, flavonoids, terpenoids, and tannins) and physicochemical test for ash value, pH value, and swelling index. The dried powder of Coelarthrum muelleri was tested for color identification with eight other reagents. The preliminary phycochemical screening of Coelarthrum muelleri showed the presence of terpenoids, steroids, tannins, saponins, phenols, coumarins, glycosides, and quinones and the absence of alkaloids. Among three extracts, ethanol and ethyl acetate extracts show all compounds present except alkaloids. Next, n-hexane showed all compounds positive except for alkaloids, saponins, and quinones, which were absent. The physicochemical indicators are 38 ml of the swelling index, 2.3 pH of 1% Coelarthrum muelleri, and 3.16 pH of 10%. The total ash value is 24.86 + 0.15%, 8.4 + 0.1% for acid insoluble ash, and 7.1 + 0.1% for water-soluble ash. This study on the present seaweed will be helpful in the identification of secondary metabolites as well as be valuable for authenticating the purity and quality.