The copyrolysis of the green microalgae Botryococcus braunii and Victorian brown coal was studied by thermogravimetric analysis using the Kissinger-Akahira-Sunose (KAS), Flynn-Wall-Ozawa (FWO), and Friedman methods. This research aims to study the synergistic effect of mixing B. braunii and Victorian brown coal in pyrolysis reactions on the kinetic parameter using thermogravimetric analysis. Copyrolysis was carried out at four heating rates, 10, 15, 20, and 25 °C/min. The copyrolysis reaction of B. braunii and Victorian brown coal occurred from 155.79 to 545.27 °C; this temperature range was lower than that for the pyrolysis of only B. braunii under the same conditions. However, mixing the two samples increased the thermal decomposition temperature for each conversion value (α), as well as the average activation energy, due to the presence of compounds that require high temperatures to undergo pyrolysis in the Victorian brown coal. The average activation energies of the copyrolysis reaction of B. braunii and Victorian brown coal determined using the KAS, FWO, and Friedman methods were 195.20 ± 17.40, 195.60 ± 17.70, and 225.93 ± 32.39 kJ/mol, respectively.